Compress PDF Files Online

Compress PDF makes your PDF files smaller so they fit email attachment limits, upload faster to job portals and government sites, and take less space on your phone or drive. The tool re-optimizes the whole document with the Ghostscript engine: images are resampled and recompressed, fonts are subset and compressed, and duplicate images are stored only once. You pick the balance between size and quality, and you see the exact result before you download.

How to compress a PDF

1. Add your PDF. Drop one or several files onto the upload area or click to choose them. Each file can be up to 100 MB.
2. Choose a compression level. Balanced is selected by default and suits most documents.
3. Adjust advanced options (optional). Set a fixed image resolution or convert the document to grayscale.
4. Click Compress PDF. When processing finishes you see the original size, the new size and the percentage saved. Download the file, or all files as a ZIP.

Compression levels explained

• Smallest file: the strongest reduction with lower image quality. Best for email, web pages and documents that will only be read on screen.
• Balanced (recommended): good visual quality with a solid size reduction, the right choice for most reports, forms and scans.
• High quality: sharper images suitable for printing on an office printer.
• Maximum quality: keeps images closest to the original. Use it when you mainly want to clean up and optimize a file without visible changes.

Under Advanced options you can override the image resolution with a fixed value of 72, 96, 150, 200 or 300 DPI instead of the automatic value from the level. 150 DPI is a good compromise for readable scans, 72 to 96 DPI for screen-only use. The Convert to grayscale switch removes colour for an even smaller file, which works well for black-and-white paperwork that was scanned in colour.

What to expect

• PDFs made of scans, photos or presentation slides usually shrink the most, because images take up most of their size.
• Text-only PDFs exported from Word or similar programs are already compact, so savings are smaller.
• If a file cannot be made smaller, the tool keeps the original size and tells you, so you never download a bigger file.
• Text stays text: it remains selectable and searchable after compression.

Tips for the smallest possible file

• Remove pages you do not need with Delete PDF Pages before compressing.
• For documents that do not need colour, Grayscale PDF or the grayscale switch here can cut the size considerably.
• If a portal limits the size of each upload, compress first, then split the PDF into parts if it is still too large.
• Password-protected files cannot be compressed; unlock them first with Remove PDF Password.

Privacy and processing

Compression runs on WoowPDF’s own servers, because the Ghostscript engine is far more effective than anything that runs in a browser. Your file is sent over an encrypted connection, processed in a temporary folder, and deleted automatically right after the compressed version is created. Files are not kept, shared or used for anything else. The service is free, requires no account and adds no watermark.

Still have the Word version and need to send that instead? Compress the DOCX file to reduce the Word file size without changing its formatting.