How to compress a PDF without losing quality

Three knobs decide whether your compressed PDF looks crisp or muddy. Here is how to think about them — and which preset to pick for email, web, or print.

# How to compress a PDF without losing quality PDF compression is mostly about images. Text is already tiny. So when a 40 MB PDF needs to fit in a 10 MB email attachment, the question is: how much image fidelity can you give up before someone notices? ## The three knobs 1. **Resolution** — measured in DPI. Screens read at ~96 DPI; print needs 300 DPI. Most "high-res" PDFs are stored at 300 even though they'll only ever be viewed on a laptop. 2. **JPEG quality** — the classic 1–100 slider. Below ~60 you start seeing blocky artifacts on gradients and faces. 3. **Subsampling** — converting 4:4:4 color to 4:2:0 halves the chroma data with almost no perceived loss for photos. ## Which preset | Use case | Pick | |---|---| | Email attachment | Medium (1.5 MB target) | | Sharing on the web | Medium / Low | | Internal archive | High | | Print bureau | Skip compression — keep the original | ## What CrispPDF does The Compress PDF tool runs all three knobs in your browser, shows you the before/after size, and never uploads the file. If the savings aren't worth it for your document, we tell you instead of pretending.