Compress PDF
Reduce PDF file size without losing quality. Shrinks images, strips unused data, and optimises fonts — your content stays identical.
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PDF only · Max 50 MB
How to Compress PDF
Drag & drop or click the area above to select your PDF file.
Your file are securely uploaded and processed on our server in seconds.
Save your result file. It's automatically deleted from our servers within 15 minutes.
3 Compression Levels
Low (best quality), Medium (balanced), or High (maximum reduction). Pick the level that fits your needs.
Quality Preserved
Text stays sharp at all levels. High compression may reduce image resolution slightly — great for documents and forms.
Before → After Report
After processing you'll see original size, compressed size, and the exact percentage saved.
What Is PDF Compression?
PDF compression reduces a file's size by removing redundant data, optimising embedded images, subsetting fonts, and eliminating duplicate objects within the document structure. The result is a smaller file that contains identical content — same text, same layout, visually the same images at normal viewing sizes.
QuickyDesk uses PyMuPDF (fitz) for compression, which applies a full optimization pipeline: garbage collection (removing unused objects), deflate encoding, font subsetting, and image downsampling depending on the compression level selected.
When to Compress PDFs
- Email attachments — Gmail limits attachments to 25 MB. Outlook defaults to 20 MB. Government and corporate email systems often enforce 10 MB or lower limits.
- Government portal uploads — Many government submission portals cap uploaded files at 2–10 MB. High-resolution scanned documents frequently exceed these limits.
- Cloud storage efficiency — Reducing the size of large document archives saves storage and speeds up sync across devices.
- Faster loading on mobile — Compressed PDFs open faster on mobile devices with limited RAM.
- Website downloads — PDFs linked from websites should be optimised for fast download. A 50 MB brochure should be under 5 MB for web distribution.
- Print shop preparation — Sending a slightly reduced file (Low compression) can still reduce transfer time without affecting print quality.
Compression Levels Explained
Low compression applies structure optimization (garbage collection, object deduplication, font subsetting) without significant image downsampling. Best for files with photographs where visual quality is a priority.
Medium compression (recommended for most files) adds moderate image downsampling, targeting screen-resolution quality. Images remain sharp at normal viewing sizes. Typically reduces file size by 40–70% for image-heavy PDFs.
High compression applies maximum image reduction. Images may appear slightly less sharp when zoomed in. Text remains crisp at all levels. Recommended for text-heavy documents, forms, and scanned documents where reducing size is the priority.
How Compression Works at QuickyDesk
- Your PDF is uploaded over HTTPS and temporarily stored on our server.
- PyMuPDF opens the file and runs the compression pipeline based on your selected level.
- Structure optimization runs first: removes unused objects, deduplicates embedded content, subsets fonts to only the characters used in the document.
- Image processing runs next: applies deflate compression to all images; Medium and High levels additionally downsample images to screen resolution.
- The optimised file is saved and staged for download. The original and compressed output are deleted within 15 minutes.
- After download, a size report shows original size, compressed size, and the percentage reduction.
Tips for Best Results
- Try Medium first. It handles the majority of cases well and is reversible — if the quality is insufficient, compress the original at Low instead.
- For scanned PDFs, use High. Scanned documents are entirely image-based and compress most dramatically at High settings.
- If your PDF is already small, don't compress it. A PDF under 500 KB is already optimised. Compression on a small file produces minimal reduction and isn't worth the round-trip.
- Never send a compressed PDF to a commercial printer. Compression reduces image resolution to screen quality, which is insufficient for print production (300 DPI minimum). Always retain the original for printing.
- Compress after merging. If you merge multiple PDFs, run compression on the merged output to reduce the combined file size before sharing.
File Requirements
- File format: PDF only
- Maximum file size: 50 MB
- Files per operation: 1
- Password-protected PDFs: Not supported
Frequently Asked Questions
What compression level should I choose?
Medium is the right starting point for most files. It balances size reduction with visual quality — images remain sharp at normal screen viewing, and text is completely unaffected. Use High for text-heavy documents, forms, or scanned PDFs where maximising size reduction is the priority. Use Low when you have photographs that need to stay at high resolution.
How much can I expect to reduce my PDF file size?
Results vary significantly by file content. Image-heavy PDFs (scanned documents, photo brochures, event programmes) typically compress by 50–80% at Medium settings. Text-only PDFs generated from Word or similar software may only reduce by 5–20% — they contain little image data to compress, and their structure is often already optimised by the export process.
Why didn't my PDF get smaller after compression?
If your PDF was already optimised when created — for example, exported from Word or InDesign at screen quality — there is little redundant data to remove. Compression cannot reduce a file below its essential content size. A 200 KB text-only PDF exported from Word is already near its minimum.
Will compression affect text readability?
No. Text in PDFs is stored as vector data, not pixels. Compression does not affect text at any level — all three settings leave text completely unchanged, fully readable, and searchable.
What is the difference between Low, Medium, and High compression?
All three levels apply the same structural optimisation: garbage collection, font subsetting, object deduplication, and deflate encoding. The difference is in image handling. Low preserves high-resolution image data. Medium downsamples images to approximately 96–150 DPI (screen quality). High applies maximum image compression and downsampling for smallest possible output size.
Can I compress a scanned PDF?
Yes, and scanned PDFs benefit most from compression. Since scanned documents are entirely composed of images (not vector text), there is substantial image data to reduce. At Medium or High settings, a 30 MB scanned document can often be brought under 5 MB without any visible quality loss at normal viewing sizes.
Is compression reversible?
No. Compression permanently modifies the file. Downsampled images cannot be restored to their original resolution. Always keep a copy of your original file before compressing — especially if the PDF may need to be printed commercially or if image quality is critical.
What is the maximum file size for compression?
The maximum upload size is 50 MB. If your PDF exceeds 50 MB, consider whether you can split it first, compress each part, then merge the compressed parts.