How to reduce a PDF's file size

Why some PDFs are so large

Text is tiny. Pictures are not. A PDF made from scans or photos stores every page as an image, so a ten-page scan can be many megabytes while a fifty-page text report can be a few hundred kilobytes. That is why the amount you can save depends mostly on what is inside the file.

A PDF that is mostly text is already compact, and no honest tool will shrink it much. A PDF that is mostly pictures can shrink a lot.

Compress a PDF step by step

1. Open the PDF compressor and choose your file (up to 100 MB).
2. Move the slider between higher quality and a smaller file. The estimated size updates as you move it, so you can see the trade-off before you compress.
3. Choose Compress PDF, then compare the result. Download it if the pages still look good.
4. If it is not small enough, go back and pick a stronger level. Your original file is never changed.

Aim for a specific size

Some forms and email systems have a hard limit, such as 2 MB. Under More options you can enter a target size. PDFScanner picks the lightest level that fits, and says so if it cannot reach the target without ruining the pages.

Keeping the text selectable

The normal levels recompress the pictures and leave the text alone, so you can still select and search it. The optional stronger compression redraws every page as a picture at a lower resolution. The file gets much smaller, but the text can no longer be selected or searched, so use it only when you must.

Make smaller PDFs from the start

• When you scan, choose Auto or Black & White for text pages. A high-contrast page compresses far better than a full-colour photo of it.
• Crop away the table and background around a scanned page.
• Avoid putting many full-resolution photos into a document when small ones will do.
• If a scan has been through several rounds of editing, going back to the original photos usually gives a smaller, cleaner result.

Check before you send

Zoom in on the smallest text and on any signature or stamp. If you can read it comfortably, the quality is fine. If not, choose a lighter level and accept a slightly larger file.