7 min read
Compress a PDF without wrecking quality
Reduce PDF size for email and portals while keeping text readable — processing stays on your device with StackPDF.
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Shrink PDF file size while keeping it readable.
How it works
- 1Add one or more PDFs from your device to the compress workspace.
- 2Wait for analysis so you can see page and image characteristics.
- 3Pick Light, Recommended, or Extreme — or set custom DPI and JPEG quality.
- 4Optionally preview quality on a sample page before committing.
- 5Run compression and compare the new size to the original.
- 6Download the smaller PDF, or keep the original if the tool reports already optimized.
About
Compress PDF files privately in your browser. Choose Light, Recommended, or Extreme — or tune image DPI and JPEG quality yourself. If nothing can shrink the file, you get your original back, never a larger version.
Most email and portal rejections come from photo-heavy scans and decks, not from plain text. StackPDF analyzes each file, re-encodes oversized images when it helps, and shows size before and after so you can pick a sensible tradeoff.
Everything runs on your device: no upload quota, no account, and no “already optimized” surprise that silently replaces your file with a bigger one.
Common use cases
- Shrink a multi-page scan so it fits email size limits
- Reduce a slide deck PDF before a portal upload
- Batch-compress receipt packets for expense systems
- Prepare a smaller archive copy while keeping a full-quality original
- Cut size after merging several image-heavy PDFs
What makes PDFs large
High-DPI phone photos, scanner images embedded at full resolution, and unoptimized JPEGs dominate file size. Duplicate fonts and leftover objects from export pipelines add weight too, but photos and scans are usually the first place to look.
Merging several heavy PDFs without an intermediate shrink multiplies the problem. Compress after merge when email or a portal rejects the combined attachment.
Light vs Recommended vs Extreme
Light and Recommended target oversized images while aiming to keep text selectable — the right default for reports you still need to search or copy from. Extreme rasterizes pages for maximum shrinkage; use it when size matters more than a live text layer.
Custom DPI and JPEG quality give finer control when a preset is almost right. Preview helps you catch blur before you download.
Privacy and when cloud compression is fine
Browser-local compression means the full document never hits StackPDF servers. That is the default choice for anything confidential.
A cloud pipeline can still make sense for automated bulk jobs, shared team storage, or server fleets processing thousands of files overnight. For one laptop and a 40 MB scan that must go out today, on-device compress is usually enough. If you still have the original photos, shrink them in StackImage Compress and rebuild with Images to PDF — often cleaner than Extreme rasterize.
FAQ
Need image tools?
Compress, convert, crop, and enhance photos in StackImage — the same privacy-first browser tools, no uploads.
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