How can a few pages be several megabytes?

Almost always because they're images, not text. A scanned page at 300 DPI is 3–5 MB before compression, and a page full of screenshots or photos is similar.

Does the number of pages matter?

For text PDFs, barely — a hundred text pages is still under a megabyte. For scanned PDFs, yes: every page carries its own image, so size grows roughly linearly with page count.

Will deleting pages help?

For a scanned PDF, a lot. Removing half the pages roughly halves the file. For a text PDF it makes little difference.

Why is my PDF so big? (and what to do about it)

Useful Hacks Team·August 29, 2026

The short version: open the PDF and look at a page. If you can select the text with your cursor, the file is probably fine and small. If the text is a picture you can't select, the file is image data — and that's why it's big. Compress PDF fixes that case.

Compress PDF

Reduce PDF file size by rendering pages as compressed images.

Open Compress PDF

The usual culprits

Scanned pages. Each page is a full-resolution image. This is the number one cause of large PDFs.
Embedded photos or screenshots. Even in an otherwise-text document, a few high-resolution images add megabytes.
Fonts. Occasionally a PDF embeds whole font files instead of just the characters used. This is usually a few hundred KB, not megabytes.
Nothing, actually. Sometimes a "big" PDF is 1–2 MB, which is completely normal and fine for email or upload. Check the real limit before optimising.

How to diagnose yours

Can you select the text? No → it's a scan or an image-only PDF → Compress PDF will shrink it a lot.
Yes, but there are big images? → compress the images with Compress Image before rebuilding, or pull them out with Extract Images from PDF to see how much they weigh.
Yes, and it's mostly text but still large? → check the page count; use Split PDF to send only what's needed.

Do it now

Open Compress PDF if it's a scan, or Compress Image for the pictures inside a text PDF.

Frequently asked questions

How can a few pages be several megabytes?: Almost always because they're images, not text. A scanned page at 300 DPI is 3–5 MB before compression, and a page full of screenshots or photos is similar.
Does the number of pages matter?: For text PDFs, barely — a hundred text pages is still under a megabyte. For scanned PDFs, yes: every page carries its own image, so size grows roughly linearly with page count.
Will deleting pages help?: For a scanned PDF, a lot. Removing half the pages roughly halves the file. For a text PDF it makes little difference.

Related guides

How to compress a PDF without wrecking it
What actually makes PDFs large, why some compressors do more damage than others, and how to pick the right approach for your file.
How to reduce PDF size without losing quality
"Without losing quality" means different things for scans and for text PDFs. Here's what's actually possible and how to get the smallest safe result.
How to convert images to PDF (JPG, PNG, phone photos)
Turn one or several JPG or PNG images into a single PDF, in the right page order — what the tool does, the steps, and the common snags.