Compress PDF
Reduce PDF file size while maintaining quality
Drop .pdf files here
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How it works
- 1. Upload your .pdf file
- 2. Enter your email address
- 3. Download your converted file
Always Free
25 free operations per year per email address. Resets every January.
About Compress PDF
Large PDF files are hard to email, slow to upload, and take up unnecessary storage. PDF Ninjas compresses your PDF by rasterising each page and re-encoding it at an optimised quality level — dramatically reducing file size while maintaining readable clarity. Image-heavy PDFs such as scanned documents, photo books, and slide exports typically shrink by 50–80%.
You can choose from three compression levels: High Quality (minimal compression, best visual fidelity), Balanced (recommended for most uses), and Max Compression (smallest possible file, suitable for archiving or emailing). The tool shows you the before and after file size so you can see exactly how much space you saved.
Compress PDF — Complete Guide
Which PDFs benefit most from compression?
PDFs that contain photographs, scanned pages, or exported slide presentations compress the most — often by 60–80%. These files have large embedded images that can be significantly reduced without any visible quality loss at normal reading sizes. Text-only PDFs (such as a typed contract with no images) will compress by 10–30% at most, since the text is already stored as efficient vector data. If you have a 10 MB scanned document that needs to fit in a 2 MB email attachment, compression is exactly the right tool.
Understanding the three compression levels
High Quality mode targets the smallest reduction in visual fidelity — ideal if you're compressing a PDF that will be printed or presented on screen at full resolution. Balanced mode (the default) produces 50–70% size reduction while keeping text sharp and images clearly legible at normal reading size. Max Compression achieves the smallest possible file but may produce visible JPEG artefacts at high zoom levels; it is best suited for archiving documents you will read digitally but not print. For most everyday email and upload needs, Balanced mode is the right choice.
After compression: check before sharing
After downloading your compressed PDF, open it and flip through a few pages at 100% zoom to check that text and images look acceptable for your purpose. If the result looks too degraded, re-compress the original using the High Quality setting rather than further compressing the already-compressed file. Repeatedly compressing the same PDF degrades quality faster than a single higher-quality compression pass. If the compressed size is still larger than expected, the source PDF may already be optimised, leaving less room for further reduction.