PDF Compressor
Compress PDF files
Click to upload or drag & drop
.pdf files only
About PDF Compressor
PDF Compressor is a free online tool that reduces the file size of PDF documents without significant loss of quality. Upload your PDF and the tool applies compression algorithms to images, streams, and metadata within the file, producing a smaller PDF that is faster to share, upload, and store.
PDF files vary enormously in size. A text-only PDF of a 10-page report might be under 100 KB. The same document with high-resolution photographs could be 50 MB or more. Large PDFs cause problems: email attachments are blocked (Gmail limits attachments to 25 MB), file upload forms reject them, cloud storage fills up, and they are slow to load and view. PDF compression solves all of these issues.
PDF compression primarily targets image data, which accounts for the vast majority of PDF file size. Images within a PDF can be resampled (resolution reduced from 300 DPI to 150 or 72 DPI) and recompressed using more efficient algorithms (JPEG compression for photographs, JBIG2 for black-and-white images). For screen viewing and most digital sharing purposes, 72–96 DPI is perfectly adequate. For professional printing, maintain 300 DPI.
Additional compression techniques include removing duplicate resources (fonts and images referenced multiple times), stripping unused metadata and embedded thumbnail images, compressing PDF content streams, and flattening transparency. These non-lossy techniques reduce file size without any quality reduction and are applied before any image resampling.
How to Use PDF Compressor
- 1Upload your PDF file
- 2Select a compression level (low, medium, high)
- 3Click "Compress PDF" to process
- 4Download the compressed PDF and compare file sizes
Frequently Asked Questions
Compression results vary hugely. A PDF full of high-resolution photos may compress from 20 MB to 2 MB (90% reduction). A text-only PDF may only reduce by 10–20% since there is little image data to compress.
Compression at medium or low levels produces minimal visible quality loss for screen viewing. High compression significantly reduces image DPI and is best for documents where images are secondary to text content.
No. Text in PDFs is stored as vector data (mathematical outlines), not raster images, so it is not affected by image compression. Text remains perfectly sharp regardless of compression level.
"Screen" (72 DPI) is smallest file size, for digital viewing only. "Ebook" (150 DPI) balances file size and quality for digital reading. "Print" (300 DPI) maintains print-quality resolution. Use "screen" for email attachments and web uploads; "print" for files that will be physically printed.
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