How-To

How to Reduce PDF File Size

April 10, 2025·5 min read

Large PDF files are a pain to share by email, upload to portals, or store in the cloud. The good news is that most PDFs contain embedded fonts, high-resolution images, and metadata that can be stripped or optimized without any visible quality loss. Here are the most effective techniques to shrink your PDFs down to a manageable size.

Why are PDF files so large?

PDFs can balloon in size for several reasons. Embedded high-resolution images are the most common culprit, especially scanned documents that store every page as a full-size bitmap. Embedded fonts, form fields, and layers also add weight. A 10-page report with photos can easily exceed 50 MB if the images were not optimized before export.

Method 1: Compress images inside the PDF

The biggest wins come from recompressing embedded images. Tools like SquishConvert can re-encode images at a lower resolution or quality setting while keeping text sharp. Dropping image quality from 300 DPI to 150 DPI typically cuts file size by 60-70% with no visible difference on screen. For print-ready files, stick with 200 DPI as a minimum.

Method 2: Remove unnecessary metadata

PDFs often carry hidden metadata such as edit history, annotations, bookmarks, and embedded thumbnails. Stripping this data can shave off 5-20% of the file size. Most PDF optimization tools let you choose which metadata to keep and which to discard. If you are sharing a final version, there is no reason to keep revision history in the file.

Method 3: Use online compression tools

Online tools like SquishConvert let you drag-and-drop a PDF and get a compressed version in seconds. No software to install. The file is processed on secure servers and deleted immediately after conversion. This is the fastest option when you need to quickly shrink a PDF before sending it.

How small can you go?

A typical 20 MB PDF with photos can usually be reduced to 3-5 MB without visible quality loss. Text-only PDFs are already quite small, but you can still save 10-30% by removing metadata and optimizing fonts. If you need files under 1 MB for email, consider splitting multi-page PDFs into smaller chunks.