How to reduce PDF file size (without ruining the quality)

You finish a report, a scanned contract or a photo portfolio, try to attach it to an email, and get a warning: the file is too large. Upload forms for job applications, public administrations and online portals often have strict limits too. The good news is that most oversized PDFs can be made much smaller without any visible difference on screen. It helps to understand where the weight comes from.

Why PDFs get so big

A PDF is a container. Text itself takes very little space; a hundred pages of plain text can weigh less than a single photo. What makes a PDF heavy is almost always something else:

• High-resolution images. A photo straight from a phone camera can be several megabytes. Put twenty of them in a PDF and the file grows accordingly, even if each image is shown at the size of a postage stamp.
• Scanned pages. A scanner does not produce text, it produces a picture of each page. A 30-page scan is really 30 large images, often saved at a resolution far higher than a screen needs.
• Fully embedded fonts. Some programs embed entire font files, including every character you never used. With several fonts, that adds up.
• Duplicated resources. When the same logo or background appears on every page, a poorly optimized export may store it again and again instead of once.

Knowing this tells you what to expect: a PDF full of photos or scans usually has a lot of room to shrink, while a text-only PDF is already small and will change little.

How PDF compression works

Our Compress PDF tool optimizes the file with Ghostscript, a long-established PDF engine. It downsamples and recompresses embedded images, subsets fonts so only the characters actually used are kept, and removes duplicate resources. Text and vector graphics are not turned into pictures, so they stay sharp and selectable, and you can still search and copy them.

The PDF is uploaded over an encrypted connection, processed on our server and deleted automatically right after processing. Files up to 50 MB are accepted, and the size reduction is shown before you download, so you know exactly what you gained. If the compressed version would end up larger than the original, which can happen with files that are already optimized, you simply get the original back.

Which compression level to choose

There are three levels, and the right one depends on what the PDF is for:

• Light keeps print quality. Use it for documents that will be printed, such as brochures, posters or photo books, when you only want to trim unnecessary weight.
• Recommended balances size and quality. It is the best default for email, sharing and online forms, and text and images still look clean on screen.
• Strong gives the smallest file by reducing images to about 72 DPI. That is fine for reading on a screen, but not for printing photos. Use it when you must get under a hard limit.

A good approach is to start with Recommended and only move to Strong if the result is still too big.

Build smaller PDFs from the start

Compression works best as a last step. If you create PDFs from photos, such as receipts, homework, a portfolio or photographed documents, you can avoid most of the bloat before the PDF even exists:

1. Resize the photos. With Resize Image you set a width in pixels and the height follows automatically, so nothing gets stretched. Around 1600 px wide is plenty for a full page on screen. Smaller images are never upscaled.
2. Compress them. Compress Image re-encodes JPG, PNG and WebP with a quality setting you control; 80% is a good default with no visible difference in normal use.
3. Combine them into a PDF. JPG to PDF places the images one per page, as they are, without recompressing them. That is why shrinking first matters: whatever size your images have is the size your PDF will have.

These three image tools run entirely in your browser, so your photos are never uploaded.

Email attachment limits

Most email services cap attachments. Gmail allows up to 25 MB and Outlook.com up to 20 MB per message. Keep a comfortable margin below those numbers: attachments are encoded for sending, which makes them larger in transit than on your disk, so a file just under the limit can still be rejected. The recipient's mail server may also have a lower limit than yours. If a document is still too big after compression, consider splitting it into several parts or sharing it through a cloud link instead.

FAQ

Will compression make my text blurry? No. Text and vector graphics stay sharp and selectable at every level; mainly images are affected.

Why did my PDF barely shrink? It was probably already optimized or contains mostly text. Such files have little left to remove.

How much smaller will it get? It depends on the content. PDFs with photos or scans often shrink by more than half; text-only files change less.

Is my document stored? No. The file is deleted automatically right after processing.