How to compress a PDF — and keep it readable

PDFs get large for predictable reasons: scanned pages saved as high-resolution images, uncompressed photos pasted into documents, embedded fonts for every variation, and years of incremental edits that leave unused objects behind. The fix depends on which of those is actually in your file.

Start with the right target

Email systems commonly reject attachments around 20–25 MB, messaging apps are stricter, and web forms often cap uploads at 5–10 MB. Aim comfortably below the limit — a file that only just fits today will bounce tomorrow when someone forwards it with additions.

DPI explained plainly

DPI here means the resolution each page is rendered at. 72 DPI is screen resolution: fine for reading on a monitor, soft in print. 100 DPI is a balanced sharing setting. 150 DPI keeps small print noticeably sharper and is a safer choice for forms and contracts. 300 DPI is print territory and rarely reduces size at all for scans.

The text trade-off

Our compressor renders pages as images, which is why it is so effective on scans — and why selectable text becomes part of the picture. If a document must stay searchable, keep the original as your master and send the compressed copy only for reading. Never overwrite your only copy.

A safe workflow

1. Duplicate the PDF.
2. Compress the copy at 100 DPI and 72% JPEG quality.
3. Open the result and zoom into the densest page — a table, a footnote, a signature block.
4. If it is soft, redo it at 150 DPI rather than raising quality alone.

Ready to try it? Use the free PDF Compressor.