About This Tool
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 Happens to Your PDF
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 You'll Need 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.
Doing It Step by Step
- 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.
Worked Examples
| Source document | Starting size | Slider setting | Typical output | Best for | |---|---:|---:|---:|---| | 15-page flatbed scan (300 DPI color) | 28.4 MB | 65% (Medium) | ~4.6 MB | Clearing a 10–25 MB email attachment cap | | 24-page slide handout with photos | 16.0 MB | 75% (Medium-High) | ~5.1 MB | Portal uploads where slide captions must stay readable | | 4-page text-only Word export | 140 KB | Any | Often larger or unchanged | Skip compression — vector text is already compact |
Quality & Limits
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.
What Usually Goes Wrong
- 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 for Best Results
- 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.
When to skip compression
Skip this tool, or stay on a light slider setting, when the PDF is going to a print shop. They need the untouched file. Skip it when a signature or stamp has to stay sharp, when the file is already small, and when you are about to compress a file that was already compressed. Start from the original export.
This tool redraws each page as an image. Selectable text, links, and form fields do not survive. If the reader has to search the PDF or fill a form, do not run it through here.
Keep a print master and compress a copy for email or a portal. A short digital letter may barely shrink. A slide deck or a long scan can drop a lot and still be the wrong file to send to a printer.
Published size examples
These examples were written for the compress guide. They live here now, next to the control that produces the file.
A four-page invoice exported at 8 MB came back at 1.2 MB on a medium setting. The text stayed readable. The logo softened slightly.
A 30-page scan at 300 dpi started at 62 MB and came back at 9 MB on medium, under a 10 MB portal cap. A chart with fine lines needed a check at a higher zoom.
A 48-page photo brochure started at 95 MB. An aggressive setting hit 12 MB and banded the sky photos. A medium setting landed at 22 MB, and the rest of the brochure stayed on a download link.
Your file will not match these numbers. The tool prints the before and after size for the upload in front of you.
OCR, then compress
If the PDF is a scan and someone needs to search it, run OCR on a clean scan before a heavy compress. Lossy compression first can wreck the pixels OCR needs.
A workable order is: scan around 300 dpi, rotate a sideways page with Rotate PDF, run OCR in the scanning software and search for a phrase you know is on the page, compress here, then search again. A PDF that already has a text layer does not need OCR. This tool removes that text layer, because it rebuilds the page as an image. Leave searchable files alone when search is the point.