How to Compress a PDF and Check File Size
Large scanned PDFs can be awkward to email or keep on a phone. PDFSwan Compress PDF rebuilds each page as an optimized image, then packages those images into a new PDF. This can help with image-heavy sources, but it changes the document structure and does not guarantee a smaller file.
Open Compress PDF ↗When to use Compress PDF
Use this workflow when a smaller visual copy is more useful than retaining searchable text and interactive elements. Do not use it as the only copy of a form, signed original, or document that needs text selection. Keep the source and compare the output size before replacing anything.
Step-by-step instructions
Load the source file
Open the Compress PDF workspace using the button above. Choose the source file from your device or drag it into the drop area. Wait for preparation to finish and check the displayed filename. Work from a copy you can retain for comparison, and clear the workspace if you selected the wrong source.
Choose Resolution
Select 96 DPI for a smaller starting point, 144 DPI for a balanced result, or 200 DPI for sharper rendering. Lower resolution uses fewer pixels, which can reduce size at the cost of fine detail. Small print is the best place to inspect that trade-off.
Set Image quality
Choose Smallest · 45%, Balanced · 65%, or High · 85%. These control JPEG image encoding. Begin with 144 DPI and Balanced, then try lower settings only if the first result is still too large and remains readable.
Download and verify the result
After processing finishes, select Download PDF. Save the new file before closing the tab or creating another result. Open the actual download in a compatible application and compare it with the source. Check the content and format you need rather than relying only on the success message.
A practical example
For an image-heavy 40-page scan, begin with 144 DPI and 65% quality. Download the output and compare its size with the source. Zoom in on a receipt number or small table. If those details remain readable, try 96 DPI and 45% for another version. Keep whichever version meets both your size target and readability needs.
Tips for a better result
Read the result message
The result reports when the file became smaller and also when the new file is larger. A compact text-based PDF may grow after rasterization, because a small amount of text becomes a full-page image. Keep the original if the output is larger.
Know what is lost
Rebuilding pages as images removes searchable text and does not preserve forms, links, or existing digital signatures. The result is a visual copy. It is not an archival conversion or a way to preserve interactive behavior.
Respect the rendering limits
Image-based tools accept at most 80 pages. A page can use no more than 16 million rendered pixels, with 160 million rendered pixels per task. Lower resolution or extract a smaller section if the task exceeds those budgets. Browser memory can still limit a job below the maximums.
Troubleshooting
Why is the compressed PDF larger?
The source may already be compact or contain efficient vector text. Try lower settings if appropriate, but keep the source when it is smaller.
Why can I no longer select text?
Compression renders the pages as images. Searchable text is not retained, and this tool does not add OCR afterward.
File limits, privacy and keeping your originals
PDFSwan processes document bytes locally in your browser without a document upload. The task limits are 50 MB total input, 60 files, and 300 PDF pages. Actual performance depends on your device and browser memory. Encrypted PDFs are rejected; choose an unlocked copy you are authorized to edit. Keep your originals, because page operations and edits may change bookmarks, forms, links, annotations, and existing digital signatures.
The home page includes Google Analytics and DeanonX site-tracking scripts. Local document processing does not mean the website has no third-party tracking. Download the result before closing the tab, and use Clear workspace to remove files from the active workspace when finished.
Frequently asked questions
Is smaller output guaranteed?
No. The result depends on source content and the selected settings.
Can I compress more than 80 pages?
This image-based workflow accepts at most 80 pages per task. Split a larger source first.
Ready to try it?
Follow the steps with a copy of your document, then check the downloaded result before sharing it.
Use Compress PDF ↗