PDF users may want their documents to be illustrative and visually-appealing, thus inserting images or graphics to the PDF. This action can lead to increased file size. However, larger PDF files can become a hindrance in file transfers and collaborations. When facing this issue, PDF compressor software helps us out.

This post gets down to the best online and desktop PDF compressors for reducing PDF file size with ease.


How to Compress PDFs with Desktop PDF Tools

First things first, you should be aware of two factors:

  1. compression technology only cuts down extra and redundant data in a PDF,and downgrades the image quality to reduce the overall file size. Users don’t have to be concerned about file integrity because no information or data will be removed or eliminated from your documents;
  2. provided that the original file size is 10 MB,and you want it compressed to or below 100 KB, note that such an action is almost impossible, and no PDF compressor can promise such an amazing compression result.

If you are looking for more advantages of a reduced PDF files, this post can help

How to Compress PDFs on Windows

For users looking for fancy PDF compressors on Windows 10, 8, or 7, our editor has reviewed commonly-seen PDF compressors and has hand-picked Windows-supported SwifDoo PDF and Foxit PDF for your reference. Let’s take a look at compressing PDF file size:

SwifDoo PDF

SwifDoo PDF is an easy-to-use offline PDF compressor. By providing three different levels of image quality, SwifDoo PDF can better meet your needs for PDF compression.


Step 1: Download and install SwifDoo PDF from the official website;

Step 2: Click Open on the home page to upload a PDF. Or, you can directly drag a PDF to the workstation;

Step 3: Click the Advanced tab to choose Compression;

Step 4: Choose the Image Quality and output destination folder. When everything is complete, click Start to export a smaller PDF file.

Note:The file size after compression is an expected value.

If in need of compressing multiple PDF documents, just press “Add Files” to perform a batch-compress task.  

                                                                      Free Download

Foxit PDF

Comparably, compressing a PDF file with Foxit PDF is more complicated than with SwifDoo PDF. That’s because Foxit PDF has incorporated advanced features within its operation panel. Users can specify which parts to compress and how images are displayed after compression.  


Step 1: Download and install Foxit PDF Editor on your PC;

Step 2: Launch the PDF program and click on the File ribbon;

Step 3: Place your cursor on the PDF Optimizer and click on Advanced Optimization;

Step 4: Change the settings if needed. When finished, click OK to complete the compression.


From the above image, users can compress the elements noted on the left column while changing the image quality should be completed in “Color/Grayscale Images” or “Monochrome Images”.  

Tips:"Reduce File Size" is a part of the "Advanced Optimization" functions. It utilizes the default settings of "Advanced Optimization".

LibreOffice Draw

Perhaps you are a stranger to this software however, LibreOffice Draw is an open source PDF compressor for Windows, Linux, and macOS. As a good PDF compressor, LibreOffice Draw reduces the image within a document so that the overall file size will be optimized. With its help, users can modify image compression level (lossless and lossy compression) and resolution (75, 150, 300, 600, and 1200 DPI).


Step 1: Download and install LibreOffice Draw;

Step 2: Launch the open source compressor and import a PDF to the workstation;

Step 3: Next,go to File and choose Export as PDF. Specify the newly created compression level and image resolution values;

Step 4: Hit the Export button to output the compressed PDF.

With this feature-rich open source PDF compressor, users can significantly optimize file size by reducing the image resolution for free.

Note:LibreOffice Draw only optimizes the size of PDF documents containing images.

How to Compress PDFs on Mac

Optimizing PDF file size is relatively simple on Mac thanks to the natural PDF and viewer editor, Preview. This build-in software integrates multiple features, such as PDF file compressing, converting, and editing. See how to reduce the file size of a PDF and save disk space on Mac:

Step 1: Open a PDF that needs compression with Preview;

Step 2: Click File and choose Export (Tip: don’t mistakenly choose Export as PDF);

Step 3: Select Quarts Filter and click on Reduce File Size in the drop-down menu.

That’s all you need to know for compressing a large PDF document without compromising quality on Mac. Though this freeware can assist in file size optimization, it can hardly batch-compress multiple PDFs at the same time. If you do need to reduce the PDF file size in bulk, consider professional online tools in the forthcoming paragraphs.

How to Compress PDFs with Online Tools

Certain users may find it annoying to download and install a desktop PDF compressor, which is fine. We do have a few excellent web-based PDF size converters for compression in this industry.


PDFCompressor is a multi-language support Internet-based compressor. The website’s design is easy to navigate without too many complicated interactive elements. It’s one of the factors that makes PDF compression so much easier on this platform:

Step 1: Type the URL in the search bar;

Step 2: Click PDF Compressor and upload the PDF to the workstation;

Step 3: Choose Download to export the compressed PDF.


This online PDF compressor supports batch processing PDF documents. If needed, click “UPLOAD FILES” to continue adding more files to the workplace.


Smallpdf is a comprehensive PDF program, which enables users to edit, convert, merge, split and compress PDF documents. It is also an online PDF compressor that simplifies the compression process with several clicks:

Step 1: Choose Compress PDF;

Step 2: Upload a PDF document from local folder, Google Drive, or Dropbox;

Step 3: Non-paying users can only tick Basic compression, then click on the Choose option to start compression.


Though it’s a free online compressor, Smallpdf allows users to perform two free tasks every 24 hours. If you need to compress a PDF to the smallest size with Smallpdf, you may hit a wall as “Strong compression” is a benefit exclusive to Pro users.  


Since PDF compression has become a frequent demand for most users, PDF developers have made compressing PDFs to desired size much simpler and have integrated more features for complicated PDF compression needs.

Common FAQ about Best Online & Desktop PDF File Size Compressors in 2021

Q:How do I use Adobe Acrobat compressor to reduce file size?

Adobe Acrobat is a powerful desktop compressor. Users can utilize PDF Optimizer options to reduce the file size.

Step 1: Open a PDF document with Adobe Acrobat DC;

Step 2: Click on the File tab, then choose Reduce File Size or Compress PDF;

Step 3: Select Save to specify the destination folder.

If you need to compress multiple PDFs at the same time, visit this website

Q:How do I reduce a PDF to 100 KB?

The file size after compression depends on the original file size. As mentioned before, if your PDF exceeds 10 MB, the smallest file size it can become is 3 MB, almost three or four times smaller than the original version. The editor used a 1.4 MB PDF for testing, and the results demonstrate that the file could be compressed to a minimum of 0.3 MB.


Roche has been an active PDF user for 6 years and tried different types of professional PDF tools (both online and desktop version) since at his bachelor degree. Now, Roche works as a columnist for SwifDoo PDF over the course of the last one year, and provides useful and practical solutions pertaining to various PDF topics for users from different features.