I Needed to Email a 47MB PDF. Here's How I Got It Under 1MB.
Last Tuesday I had to email a contract to a client. The PDF was 47MB because the designer embedded full-resolution photos on every page. Gmail caps attachments at 25MB. Google Drive sharing was "too complicated" for this particular client (his words). I needed that file smaller. Fast.
After trying five different methods, I got it down to 800KB with barely noticeable quality loss. Here's everything I learned, ranked from "easiest" to "nuclear option."
Method 1: Online compression tools (the easy way)
For most people, this is all you need. Upload your PDF, pick a compression level, download the result. Tools like our PDF tools or Adobe's online compressor handle this well.
I threw my 47MB file at three different online tools. Results:
- Tool A: 47MB → 8.2MB (83% reduction, some image blur on zoom)
- Tool B: 47MB → 12MB (74% reduction, images looked identical)
- Tool C: 47MB → 4.1MB (91% reduction, images noticeably degraded)
The sweet spot for most files is 70-85% compression. If a tool promises 95%+ reduction, your images are getting destroyed.
Method 2: Re-export from the source
If you have the original file (Word, InDesign, whatever), re-exporting with optimized settings is usually better than compressing after the fact. In Word: File → Save As → PDF → "Minimum size (publishing online)." In InDesign: Export → PDF → set image quality to "Medium" instead of "Maximum."
This got my file from 47MB to 3.8MB because it resampled images during export instead of trying to compress already-embedded ones.
Method 3: Ghostscript (for nerds)
If you're comfortable with the command line, Ghostscript gives you the most control. The magic command:
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=small.pdf big.pdf
The -dPDFSETTINGS flag controls quality: /screen (smallest, ugly), /ebook (good balance), /printer (high quality, larger). For email, /ebook is usually perfect.
This is what finally got my 47MB file to 800KB. The text was perfectly crisp and the images were good enough for screen viewing.
What doesn't work
Zipping the PDF: PDFs are already compressed internally. Zipping a 47MB PDF gives you a 46MB zip. Useless.
"PDF optimizer" browser extensions: Most of these just upload your file to a random server and compress it there. Same result as Method 1, but with bonus privacy concerns.
Splitting into multiple files: If someone asks me to "just split it into 3 parts," I'm finding a new client.
The quick decision tree
Need it under 10MB for email? Online compression tool, medium quality. Takes 30 seconds.
Need it under 2MB for a web form? Re-export from source if you have it. Ghostscript if you don't.
Need it under 500KB? You're going to lose some image quality. Accept it. Or convince the recipient to use a file-sharing link instead.