in Marketing How To Reduce the File Size of a PDF So you have a PDF file that’s just a little too big (or really too big!) to send over email. Or upload. What do you do? Luckily, there are several ways to compress a PDF file without sacrificing quality: Compress the file using Adobe Acrobat Pro Compress it on your computer Compress the file using an online compression tool. Compress it on WinRAR. So, there a number of ways to reduce file size, but some methods are more effective than others.