Large PDF files take spaces and occupy a lot of resource of network when you upload or send it by email. So, very often, we need to compress the PDF files.
Though there are numerous online PDF compressors, just a few can compress a PDF file up to 80% or more, even below 100 KB. After countless testing on different PDF compressors online, here we list 5 best online PDF compressors to compress PDFs to 100 KB and an ultimate tool to reduce your PDF file size to 200KB, to 100KB without losing quality.
Cisdem PDF Compressor
Free Download Windows 11/10/8/7 
Free Download macOS 10.15 or later
Actually, most of online free PDF compressors can make your PDFs up to 60%~90% smaller, but if you want more, like reducing your PDF files by 98% or processing PDFs without losing quality, you will need a professional PDF compressor.
Cisdem PDF Compressor is a program to compress large PDFs to 100 KB or below 100 KB, even up to 98%, it can batch compress dozens of PDF within seconds. There are 4 compression modes: Small (72 ppi image), Medium (150 ppi image), Large (200 ppi image), Custom (1~300 ppi image).
Free Download Windows 11/10/8/7 Free Download macOS 10.15 or later 
Online2PDF Compressor is the only one online PDF compressor that can compress my 11.8MB-PDF file to 98KB. Its powerful compression capability results from different compression modes and settings to downsize a PDF as much as possible. In addition, this online PDF compressor provides a brief interface, you can click “Select File” button to add your PDF file or just add by drag-n-drop. Furthermore, PDF Compression allows users to select several files at once.
iLovePDF can make your PDFs up to 90% smaller, you can compress PDF files from your local folder, Google Drive or Dropbox. There are 3 compression levels available: extreme compression (less quality, high compression), recommended compression (good quality, good compression), less compression (high quality, less compression). However, you can compress PDF one by one, 2 or more PDF compressions requires registration.
FreePDFConvert Compressor provides 4 ways to add PDF files, including My Computer, Dropbox, Google Drive and URL. This web-based compressor is very simple to use. You are allowed to reduce your PDF files by 50% (Good Compression Mode), by 80% (Extreme Compression Mode) or with Custom Compression. Yet, it doesn’t support batch compress PDF online free.
PDF Compressor is another online free PDF Compressor for mac which will help users to compress PDF file easily without any downloading and installing. What you need to do is select PDF files from your computer or drag them to the drop area. And then wait until the PDF compression is completed. PDF Compressor allows you to download each file individually, or you can download all of your files at once in a ZIP archive.
PDF2Go Compressor offers 3 compression modes too. And its custom mode is very powerful, by giving users 6 options to compress their PDF files basing on image quality: 20dpi/ 40dpi/72dpi/150dpi/300dpi/300dpi with color preserving. Still, you can compress and save all pages in grayscale. It supports batch compress.
All online free PDF compressors for mac can work with any browser and they are all easy to use. But when talking about compression spread and compression quality, a professional PDF compressor would be more instrumental.
Free Download Windows 11/10/8/7 Free Download macOS 10.15 or later
Carolyn has always been passionate about reading and writing, so she joined Cisdem as an editor as soon as she graduated from university. She focuses on writing how-to articles about PDF editing and conversion.
Walter
Why is there always a size limit for PDF compression with online service? Mine is often in large size, what a pain.
Juan
Useful!!!
Steve43
I wanted to compress my PDF recently, and I tried a free tool. It is really free and useful. Thank you for sharing.