Compress PDFs online fast and free

A smart cloud solution for easily reducing PDF files’ size while retaining quality
Drag & Drop the File(s) Here

Safe and secure

Quick and easy

No email



File extension .pdf
Internet media type application/pdf
Description: PDF is the Portable Document Format developed by Adobe Systems. It was invented to streamline the process of sharing and viewing files independent of any software, OS or hardware. Individuals can use PDFs wherever and whenever they want on any device. PDF files can contain textual and visual data as well as links, buttons and more. PDFs can be also password protected and edited with special programs.
Technical Details: Graphics are represented in PDF very similarly to that of PostScript. PDF graphics use a device-independent Cartesian coordinate system which describes the surface of a page. The page description uses a matrix to scale, rotate, or skew graphical elements. The graphics state is a collection of graphical parameters that may be changed, saved, and restored by a page description.
Developed by ISO
Initial Release: 15 June 1993
Useful links:

Compress PDF files online for free without quality loss

How to reduce the size of a PDF document online


Massive documents can bring many difficulties. Tutorials, manuals, reports, and books are often too large for sharing and take up too much space on your devices. When searching for ways to resize documents, it's important to choose one that shrinks them enough while also preserving their quality. We recommend our cloud-based PDF compressor. Follow the instructions below to make your files smaller, yet retain their high quality. 

How to reduce a PDF’s size online

  1. Drag and drop a file for compression from your hard drive or the cloud.
  2. Click Compress Now! to shrink your PDF.
  3. Use the Download Now button to save the newly created document.
  4. Choose one of the extra options to edit, e-sign, save, or share.
  5. Click Start over again to resize another file.

That’s it. With our platform, it’s as easy as a piece of cake. It only takes a few seconds and clicks to reduce a PDF’s size. Your new document will be optimized enough for sharing and retain its high quality. There are no limits on the number of documents you can compress. Use our service anytime as much as you need, free of charge, and without having to register an account. For more features related to PDF management, check out AltoPDF’s suite of other tools: editing, annotating, rotating, merging, e-signing, and much more. 

Watch our video guide on how to compress a PDF online

Take a look at the quick video tutorial on how to easily reduce a PDF’s size online. The service is fast, secure, and absolutely free. Learn how to shrink documents without compromising their resolution. Save time and storage space!

The Ultimate Features Comparison Chart

With so many tools on the market, it’s hard to choose the right one. Most of them seem similar until you look deeper. Use our comparison table to compare the market leaders in PDF management. Find out why choosing AltoPDF is a smart decision not only for reducing file size but for many other actions as well.

View & edit
Split PDF
Merge PDF
Combine & Reorder
Extract Pages
Compress PDF
Rotate PDF
No software downloads
Cloud storage Unlimited No info No info
Price Free Free 7-Day Trial paid Free 7-Day Trial paid
Encryption and security
Support 24/7/365 No info
No ads

Customer Reviews — Trusted by great people

⭐ ⭐ ⭐️ ⭐️️ ⭐️

Excellent solution! If the size of your PDF document is too big, reduce it with just a few clicks. It solves the memory shortage problem. Plus it’s so quick!



⭐ ⭐ ⭐️ ⭐️️ ⭐️

What I like best about the AltoPDF tool is that no registration is required. Creating an account is one of those things that makes me wanna leave the website.



⭐ ⭐ ⭐️ ⭐️️ ⭐️

That’s awesome! I can compress my PDF files from any device, even when I’m in a taxi or on a buss, or walking on the street. It take up memory cause no installations are needed.



Your opinion matters!

If your experience was picture-perfect, please take a moment to tell us so.

How To Compress a PDF File

Using this service everyone can decrease the size of the PDF file in several simple steps. Just open the website and compress the document from any device.

How to compress a PDF online

The best solution for PDF compression is our online tool. It doesn't require any installation and, thus, doesn't take up internal storage space. From the vast range of services, we recommend choosing AltoPDF. It's simple in use and does its job quickly, reducing any file’s size in a flash. Moreover, it preserves the good quality of images and text, getting you the same document but smaller. 

Make your PDF smaller in size online:

  1. Open in any browser.
  2. Browse for a sample from your device with the Choose File button or upload one from Dropbox, Google Drive, or One Drive.
  3. Click Compress Now to reduce the selected sample’s size. 
  4. Download the result. 
  5. Click Start over again to optimize another document.

It only takes a couple of clicks to reduce a PDF’s size without compromising its quality. Because AltoPDF is a cloud-based platform, it keeps your data safe from being viewed or stolen by third-parties and deletes it right after the page is refreshed or the popup window is closed. There’s no limits on the number of compressions you can make, use it all day every day. Plus, it’s free of charge and doesn’t require any installation or registration. Explore its advantages now!

BackgroundHow to compress a PDF online

How to compress a PDF in Google Chrome

There’s a faster and more professional way to compress PDFs online than searching for a particular webpage every time you need it. If you prefer working in Google Chrome, try using extensions. These small programs are embedded into the browser and allow you to get access to the tools by clicking on their icons. It's very convenient if you work with PDFs every day and need to decrease their sizes often. Install the AltoPDF compressor to decrease your files’ size any time. 

Use the guide below:

  1. Go to the Google Chrome Web Store in your browser’s settings, search for AltoPDF’s extension, and set it up.
  2. Click on the extension’s icon at the top right side of the screen to launch it. 
  3. Select a sample for reduction by clicking the Choose File button.
  4. Wait while it processes, click Compress Now! The form will be reduced automatically.
  5. Download the newly created document. 

With the AltoPDF browser tool, you can reduce a PDF file’s size fast and easy from any device. There's no need to switch between tabs; it's available whenever you need it. No software installation, registration, or watching ads. Plus it's free! Is there anything more convenient and beneficial? Try it now!

BackgroundHow to compress a PDF in Google Chrome

How to compress a PDF in Windows

It seems strange, but being one of the most popular OSs in the world,  Windows still doesn’t have built-in software for editing forms in Portable Document Format. Of course, you can easily view PDFs with the default Edge browser, but it doesn't allow you to modify them, convert them to other formats, or change their size. To do so, you'll have to install additional programs on your device or use online services. Should you need to diminish your forms for better storing and sharing without installing third-party solutions, we recommend you try AltoPDF, our free online tool. 

Follow these simple instructions to compress PDFs online:

  1. Open any browser and navigate to
  2. Upload a sample by browsing for it on your device or by importing it from the cloud.
  3. Click Compress Now! and wait a few seconds while it processes. 
  4. Click Download Now to save the copy.
  5. Use the Start over again option to work on another sample.

With our tool, reducing a PDF file’s size is fast and easy. No need to use other tools or adjust any settings. The compression is automatic, and you'll get an optimized document with preserved quality. Plus, it’s absolutely free. No need to register an account or watch annoying ads. Give it a try and compress your files in just a few clicks!

BackgroundHow to compress a PDF in Windows

How to compress a PDF on a Mac

Unlike Windows, macOS features built-in software for viewing PDFs and images and even basic editing. So Mac users are luckier for being able to modify forms in Portable Document Format without searching for third-party solutions. If your files are too large to share via email or you want to save as much space on your device as possible, use Preview to compress PDFs. It's safe, free, and simple to do.

Just follow this step-by-step guide:

  1. Open your sample with Preview.
  2. Click on the File menu and select the Export option. 
  3. Rename your file or leave it as it is.
  4. Select Reduce File Size from the Quartz Filter in a new dialog box.
  5. Click Save and select the location for your new form.

Check the new sample and you’ll notice that the quality hasn’t been altered. Shrinking PDFs with Preview is easy and straightforward. If you work a lot with forms in Portable Document Format on a Mac, this way of optimizing their size is convenient. It doesn't require any extra tools and will help you even if you don't have a stable internet connection. But if you prefer working online or need to modify a document from the cloud, take advantage of AltoPDF’s cloud-based tool for compressing PDFs for free. It's a secure service that does its job fast. Try it now!

BackgroundHow to compress a PDF on a Mac

How to compress PDF in Adobe Acrobat

Acrobat Reader is one of the most popular software for managing forms in Portable Document Format. And it's no surprise since it's a product of Adobe Systems, the creators of PDF. It features many tools for editing, converting, and size adjustment. The program has both a desktop application as well as an online version. However, it requires registration and has a limited trial that only lasts 7 days. After that, you'll need to buy a full subscription.

Follow the steps below:

  1. Download the program from Adobe’s official website.
  2. Launch it and open your sample. 
  3. Click on File in the top menu bar and select Reduce File Size from the drop-down list.
  4. Compress the PDF with the appropriate button. Use Advanced Optimization for extra settings. 
  5. Select the location and folder for your newly-created file and click Save

Acrobat Reader has many advantages. It's safe-to-use and contains advanced options for shrinking documents. It's also convenient if you constantly need to manage forms in Portable Document Format. However, if it’s something that you do once in a while, paying for a subscription can be costly. We recommend you try online tools, like AltoPDF. It's a cloud-based platform that’s free and secure. Make PDF compression fast and east, without having to install software or register an account. Try it now!

BackgroundHow to compress PDF in Adobe Acrobat

How to compress a PDF on mobile

Nowadays, many people have to complete and send documents while on the go, using their smartphones. Emailing large-sized forms can be complicated due to limits associated with attachments. If you frequently receive files in Portable Document Format and have to manage them right from your mobile device, we have a great solution for you. Compress PDFs online for free with AltoPDF. This cloud-based tool allows you to make forms smaller in just a few clicks. It doesn’t require any installation or registration. All you need is an internet connection and several seconds to complete the compression.

See how to easily adjust your samples on mobile:

  1. Go to
  2. Browse your samples and choose one by clicking the Choose File button.
  3. Tap Compress Now!.
  4. Download the new form or choose whether to continue editing or e-signing it.
  5. Tap Start over again if you have more documents to shrink. 

The AltoPDF tool helps you easily reduce PDF file sizes without compromising their quality. Based in the cloud, it works fast and keeps your data safe, deleting it right after the page is refreshed or after the popup window is closed. Optimize your device’s storage for free, no installation, registration, or annoying ads. Give it a try!

BackgroundHow to compress a PDF on mobile

How to compress a PDF on iOS

Working with large files, especially on an iPhone or iPad can use up your available space very quickly. When you process forms in Portable Document Format on the go, it's important to reduce their size for more effective storage. For iPhone users, there're various applications in the App Store for such purposes. Though, if you want to save your phone's memory, installing additional software isn't the best idea. Reduce a PDF file’s size fast and hassle-free online, with AltoPDF.

Find out how to make your forms smaller in seconds:

  1. Open Safari or any other browser and go to 
  2. Upload a document using the Choose File option.
  3. Delete a template you accidentally uploaded by tapping on a Trash icon. 
  4. Tap Compress Now! and wait a couple of seconds until the process is complete.
  5. Download the sample to your device or to the cloud. 

AltoPDF is a web-based tool that allows you to make as many documents smaller as needed, any time, and on any iOS device. Protect your sensitive data from being copied or lost. Compress PDFs’  while preserving their original quality and optimize your device’s space. It's free and doesn’t require installing extra software or signing up for an account! Try it now and experience the benefits!

BackgroundHow to compress a PDF on iOS

How to compress a PDF on Android

Being able to edit forms right from your smartphone and tablet is a huge timesaver. The problem is most documents like contracts, agreements, instructions, etc., are usually large in size. Saving them on your device can cause issues with storage. Make them smaller before saving them. For Android OS users, there are some applications available in the Google Play Market but those also take up memory. Compress PDFs for free online, instead. Check out AltoPDF. 

Follow these quick steps to make your document smaller:

  1. Open in your browser.
  2. Upload a sample from your smartphone or the cloud. If the wrong one was selected, use the Trash bin icon to delete it and restart.
  3. Tap Compress Now!. The chosen file will be reduced in several seconds.
  4. Download it to your mobile device or export it to the cloud.
  5. Continue modifying the newly-created form by tapping the Edit, Sign And Secure, or Share buttons.

Using our tool, you get an optimized document in terms of size with preserved quality. It's simple-to-use, fast, and free! No need to have an account or install anything. Reduce a PDF file’s size anytime from any device. Get started today!

BackgroundHow to compress a PDF on Android


How do you reduce the size of a PDF?

There are several ways to reduce a PDF file’s size but the best one is to use an online compressor. Try AltoCompressPDF to quickly and securely make your files smaller. Just drag and drop a document into the highlighted field and click Compress Now!. It’s absolutely free and in seconds, you’ll get a new file.