Introduction
Large PDF files clog inboxes, exceed upload limits, and slow down websites. Compress PDF reduces file size by re-rendering each page and applying JPEG compression at a level you control. The entire process runs in your browser — nothing is sent to a remote server.
What This Tool Does
After you upload a PDF, the tool renders each page to a canvas using pdf.js, converts the result to a JPEG image at your chosen quality level, and rebuilds a new PDF with pdf-lib. A compression slider lets you balance file size against visual fidelity. When processing finishes, you see both the original and compressed file sizes so you can judge whether the result meets your needs.
When to Use It
- Email attachments — Shrink a report or presentation to fit within your provider's size limit.
- Website uploads — Reduce portfolio PDFs or product catalogs before publishing online.
- Cloud storage — Free up space by compressing archived scans and photo documents.
- After merging — Combine files with Merge PDF first, then compress the final output once.
Step-by-Step Guide
- Upload your PDF to the drop zone.
- Set the compression level using the slider — start around 60–75% for a balanced result.
- Click Compress and wait. Large files with many pages take longer because each page is rendered individually.
- Compare file sizes displayed after processing.
- Download the compressed PDF and review it before deleting the original.
Limitations
Because compression works by converting pages to images, the output loses selectable text, hyperlinks, and form fields present in the original. Documents that are already mostly text with embedded fonts will not shrink much — the tool is most effective on scanned pages and image-heavy layouts. At the lowest quality settings, small text and fine details may become hard to read.
Common Mistakes
- Compressing an already-compressed file — Running the same PDF through compression again rarely helps and can degrade quality further.
- Using aggressive settings for print — A 30% compression level may be fine for screen viewing but unsuitable for professional printing.
- Skipping the visual check — Always open the compressed file and zoom into text and images before sharing or deleting the original.
- Expecting lossless results — This tool trades some fidelity for size. For lossless optimization, desktop tools with object-stream rewriting are a better fit.
Tips
- Start with medium compression and increase or decrease based on the size reduction shown.
- Compress after merging multiple files rather than compressing each file individually — you get one pass and a single result to review.
- For documents with only a few image-heavy pages, consider splitting those pages out, compressing them, and merging back.
- If the compressed file is still too large, try PDF to JPG for individual pages you need to share as images instead.