How to Compress a PDF Online
- Upload your PDF file using the box above.
- JustPDF recompresses the images inside the file and strips unused objects.
- See your before/after file sizes and download the compressed PDF.
All processing happens in your browser — your files are never uploaded to any server.
How Does PDF Compression Work?
JustPDF reduces file size by recompressing the images embedded in your PDF — decoding each one, scaling down anything unusually large, and re-encoding it at a lower quality — and by stripping unused objects from the internal document structure. The text layer is left untouched, so text stays sharp, selectable, and searchable. For scanned documents with little real text, JustPDF switches to maximum compression and rebuilds every page as an image: that shrinks the file much further, but the text is no longer selectable. The result panel tells you which mode was used.
When to Compress a PDF
- Email attachments that exceed size limits
- Uploading documents to portals with file size restrictions
- Sharing large reports or presentations
- Archiving documents to save storage space
Frequently Asked Questions
Will compression reduce quality?
Images are re-encoded at a slightly lower quality, and very large ones are scaled down — at normal viewing size this is usually not noticeable. Your text is not touched: it stays sharp and selectable. If your document is a scan that needs maximum compression, JustPDF rebuilds the pages as images, which shrinks the file the most but leaves the text non-selectable.
How much smaller will my file be?
It depends on what is inside the PDF. Image-heavy and mixed documents typically shrink by around 60%, and scanned pages by 80-90%. PDFs that are almost entirely text have very little to remove and come back close to their original size — never larger.
Can I compress multiple files at once?
Currently, you can compress one file at a time. Batch processing is available with a Pro subscription.