Reduce PDF File Size
Large PDF files cause real problems — email servers reject them, upload portals refuse them, and sharing them eats through storage limits. Whether you have a scanned document, an image-heavy report, or a presentation exported to PDF, this guide explains how to compress it effectively and what results to realistically expect. Our compressor runs entirely in your browser, so nothing gets uploaded to any server.
Why Reduce PDF File Size?
PDFs grow large quickly when they contain photographs, illustrations, or pages scanned at high DPI. A single scanned page at 300 DPI can weigh 1–3MB, so a 20-page document easily reaches 30–60MB — well above what email and many web portals allow.
Common scenarios where file size becomes a blocker:
- Email attachments — Gmail limits attachments to 25MB; Outlook to 20MB. Anything close to these limits slows delivery and often gets blocked.
- Government and university portals — Many submission forms cap uploads at 2–10MB per file.
- Cloud storage — Smaller files reduce sync time and stay within free tier quotas.
- Sharing via messaging apps — WhatsApp, Telegram, and Slack all have file size limits that large PDFs frequently exceed.
How Much Can You Actually Compress a PDF?
The answer depends almost entirely on what is inside the PDF:
Text-only PDFs
Documents that contain only text and simple vector graphics are already compact. Compression typically reduces these by 5–20%. If your PDF is mostly text and already feels small, don't expect a dramatic reduction — there simply isn't much to squeeze.
Image-heavy PDFs (reports, brochures, presentations)
PDFs with embedded photos or illustrations compress very well. Reducing embedded image quality from print-ready (300 DPI) to screen resolution (72–150 DPI) typically cuts file size by 40–70% with no visible quality difference on screen.
Scanned PDFs
Scanned documents are entirely made of raster images, making them the best candidates for compression. High compression settings can reduce these by 60–90%. A 50MB scanned contract can routinely become 5–10MB without losing legibility.
Tips for Maximum Compression
Getting the best results from PDF compression isn't complicated, but a few practices help:
- Choose a higher compression level. The High or Maximum setting reduces embedded image quality more aggressively. For documents that will only be read on screen, this is almost always acceptable.
- Check if the PDF is already compressed. Some PDFs exported from Word or created by modern printers are already optimised. If a 2MB PDF barely shrinks, it was likely compressed at creation.
- Split before compressing. If you only need to send part of a large PDF, use a PDF splitter first to extract the relevant pages, then compress that smaller file.
- Re-scan at a lower DPI. If compression still leaves the file too large, the original scan resolution may be extremely high. Re-scanning at 150–200 DPI instead of 300–600 DPI dramatically reduces the starting file size.
Frequently Asked Questions
What is the maximum compression achievable for a PDF?
It depends heavily on content. Image-heavy and scanned PDFs can compress by 50–90%. Text-only PDFs are already compact and may only reduce by 5–20% since text data compresses very efficiently at creation time.
Will text quality be affected during compression?
No. Text and vector elements in a PDF are not degraded during compression. Only embedded images may have their quality slightly reduced depending on the compression level you choose.
Does this tool work on scanned PDFs?
Yes. Scanned PDFs are essentially image containers, so they benefit the most from compression — often shrinking by 60–90% at high compression settings.
Is my PDF uploaded to a server?
No. The entire compression process runs locally in your browser. Your PDF never leaves your device, which means your documents stay completely private.