How to reduce PDF file size

A PDF that is too big to email or upload is almost always big because of images. Here is how to make it smaller without breaking it.

By 孤獨的時空旅人 · Updated 2026-09-29

Why is my PDF so large?

Text and vector graphics take very little space. Most of the size comes from photos and scanned pages, which are stored as images inside the PDF. A 20-page scan made on a phone can easily reach 30–50 MB, while the same pages as digital text would be a few hundred KB.

Embedded fonts and duplicated images add a little more, but they are rarely the main reason.

Step 1: Try the text-preserving compression

Open Compress PDF and keep the default mode. It re-saves the file more efficiently and keeps text selectable and searchable, so it is safe for contracts, forms and anything someone may need to copy from. The result shows the size before and after.

Step 2: Use strong compression for scans

If the file is mostly scanned pages or photos, choose the strong mode. It turns every page into a compressed image, which usually shrinks scans dramatically. The trade-off: text can no longer be selected or searched, so keep the original if you need that.

Step 3: Split the file if it is still too big

Many email services cap attachments at around 20–25 MB, and online forms often allow only 2–10 MB per file. If one file is still over the limit, use Split PDF to send it in parts, or extract only the pages the recipient actually needs.

Rebuilding a scanned PDF from photos

If you still have the original photos, you can often get a smaller and cleaner PDF by starting again: crop away the edges, compress the images, then combine them with JPG to PDF. Photos from an iPhone may be HEIC — convert them to JPG first.

Tools used in this guide

Compress PDFMake PDF files smaller Split PDFExtract pages or split by range Compress ImageShrink JPG, PNG and WebP files JPG to PDFTurn photos and images into a PDF

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