Most email services refuse attachments above about 20 to 25 MB, and many company mail servers stop at 10 MB. A scanned contract or a report full of photos passes that limit easily. Here is what makes a PDF large and how to bring it down.
What makes a PDF large
Text costs almost nothing. A 100-page text-only report is often under 1 MB. The size almost always comes from pictures inside the file:
- Scans and phone photos. Every scanned page is a full photo, often taken at a much higher resolution than needed for reading.
- Photos pasted into documents. A 12-megapixel photo inserted into a Word file and saved as PDF keeps its full resolution, even if it shows as a small picture on the page.
- Embedded fonts. These add some size, but rarely more than a few hundred KB.
Two ways to compress, and which to choose
PDF Safehouse's Compress PDF tool has two modes:
- Keep text selectable (recommended). Only the pictures inside the file are resized and re-saved at a sensible quality. Text stays real text, so you can still select, search and copy it. This usually removes most of the size of a scanned or photo-heavy file.
- Convert pages to images. Every page is turned into a single image. This always produces a predictable size, but the text can no longer be selected or searched. Use it only when the first mode cannot get the file small enough.
If you need the file under a specific limit, type the target size (for example 9000 KB for a 10 MB limit). The tool tries progressively lower picture quality until the file fits.
Step by step
- Open Compress PDF and choose your file.
- Keep Keep text selectable chosen and the quality on Balanced.
- Optionally enter a target size a little below your email limit.
- Download the result and open it once to check that it still reads well.
When a PDF will not shrink
If the tool says there are no large images to shrink, the file is mostly text and vector drawings and is already efficient. A few options remain:
- Split it. Use Split PDF to send it in two or three emails.
- Remove pages nobody needs, such as blank pages or appendices, with Remove pages.
- Share a link instead of an attachment with a cloud storage service you already use.
Tips for smaller files from the start
- When scanning paper documents, grayscale or black-and-white is enough for text. Colour scans are several times larger. The Scan to PDF tool has a black-and-white mode made for this.
- Before putting photos into a document, resize them. A picture that appears 8 cm wide on the page does not need to be 4000 pixels wide.