Many government websites have this PDF file size restriction, that doesn't allow you to upload a PDF with a file size more than a certain limit. That leaves a person with only one option, i.e. to compress the PDF and reduce its file size; but how do you do that? In this guide, we take a look at some of the best methods that let you compress PDF files. The best part is that these methods are absolutely free and are supported on all major operating systems. Keep reading as we tell you how to compress PDF files on your computer and phone.