How to compress a PDF
A scanned document weighs 15 MB. A report with high-resolution images can reach 50 MB. Most email services limit attachments to 25 MB. This guide shows you how to reduce PDF file size effectively.
Why are PDFs so large?
A PDF can contain much more than text. Here's what makes them bloat:
- Embedded images. This is the #1 cause. A PDF created from scans contains full-resolution images (300 dpi) weighing several MB each.
- Embedded fonts. To ensure correct display, PDFs often embed the fonts used (500 KB to 2 MB per font).
- Metadata and annotations. Comments, form fields, embedded attachments… each element adds weight.
- Accumulated versions. Successive modifications to a PDF add data without removing the old (incremental saves).
Compression levels
Filzy offers multiple compression levels to suit your needs:
Low compression
Reduces size by 20–40%. Preserves maximum image quality. Ideal for documents intended for printing or legal archiving.
Recommended compression
Reduces size by 40–70%. Good balance between size and readability. Perfect for email or online sharing.
Maximum compression
Reduces size by 60–85%. Images are noticeably degraded but text remains perfectly readable. For documents where only text content matters.
Tutorial: compress a PDF with Filzy
Open the tool
Go to Compress PDF.
Drop your PDF
Drag and drop your PDF file into the zone. Filzy shows a preview of the first pages and the current document size.
Choose the compression level
Select the level suited to your use. For email, recommended compression is usually sufficient. For an official document, prefer low compression.
Start compression
Click "Compress". Processing recompresses embedded images and optimizes the PDF's internal structure. Everything happens in your browser, no file is sent.
Check and download
Filzy displays the before/after size and reduction percentage. Verify the result is satisfactory, then download the compressed PDF.
How to get the best results
- Scanned PDFs. These are the best candidates. Scans contain very high-resolution images that easily compress by 60–80%.
- PDFs with few images. If your PDF is mostly text, the gain will be modest (10–20%). That's normal: text already weighs very little.
- Already compressed PDFs. Recompressing an already optimized PDF will yield little gain. If Filzy shows less than 10% reduction, your file is probably already well optimized.
- Combine with other tools. After compression, you can merge with other documents or protect the result with a password.
Common size limits
To help you choose the right compression level, here are common limits:
| Service | Attachment limit |
|---|---|
| Gmail | 25 Mo |
| Outlook | 20 Mo |
| WhatsApp (document) | 100 Mo |
| Impôts (télédéclaration) | 10 Mo |
| Pôle Emploi / CAF | 5 Mo |
Your documents stay private
PDF compression happens entirely in your browser. No document is sent to a server. Your invoices, contracts, and personal documents never leave your device.