How to Reduce PDF Size for Email Attachments
"Your attachment is too large." We've all seen this frustrating message. This guide covers practical techniques to shrink PDFs so they fit within email attachment limits.
Common Email Attachment Limits
Before diving into compression, it helps to know what you're working with:
| Email Provider | Attachment Limit |
|---|---|
| Gmail | 25 MB |
| Outlook.com | 20 MB |
| Yahoo Mail | 25 MB |
| Corporate Exchange | 10-20 MB (varies) |
| iCloud Mail | 20 MB |
Note: A lot of corporate email systems are even stricter—sometimes as low as 5-10 MB. Worth checking with IT or asking your recipient if you're not sure.
Quick Fixes: Low-Effort Solutions
1. Split the PDF
Got a 50-page document? Consider splitting it into smaller chunks. A 100MB PDF split into 4 parts of 25MB each can be sent as separate emails. Doesn't reduce total size, but it works around the limits.
2. Send Only Relevant Pages
Does your recipient really need all 47 pages, or just pages 5-10? Extract only what they actually need—can cut file size dramatically. Be thoughtful about what you're sending.
3. Use a Cloud Link Instead
Upload the PDF to Google Drive, Dropbox, or OneDrive and share a link instead of attaching the file. This bypasses attachment limits entirely. Most modern email clients even offer this automatically when attachments are too large.
Compression Techniques
When you truly need a smaller file (not just a workaround), here's how to achieve it:
Technique 1: Image Quality Reduction
Most PDF size comes from images. Reducing image quality is the most effective way to shrink files:
- High quality (screen): 150 DPI, suitable for on-screen viewing
- Medium quality (ebook): 100-150 DPI, good balance
- Low quality (minimal): 72 DPI, very small files but noticeably lower quality
A PDF with photos at 300 DPI can often be reduced to 150 DPI with minimal visible impact when viewed on screen. Print quality will suffer, but for email review purposes, it's usually fine.
Technique 2: Grayscale Conversion
Color images use 3-4 channels of data; grayscale uses just one. Converting color to grayscale can reduce image sizes by 60-75%. Use this when color isn't essential to the document's purpose.
Technique 3: Remove Metadata and Hidden Content
PDFs from design software often contain:
- Edit history and version tracking
- Hidden layers and objects
- Embedded color profiles
- Thumbnails and navigation data
- Form field definitions
Stripping this hidden content can reduce file sizes without affecting visible quality.
Pro Tips for Maximum Reduction
- Scanned documents are often the worst offenders—try higher compression
- Re-export from the source application with smaller settings before compressing
- Combine techniques: grayscale + lower DPI + metadata removal
- Test the result before sending to ensure readability
What to Expect: Realistic Size Reductions
Compression results vary dramatically based on the original PDF:
- Text-only PDFs: Already small, limited compression possible (5-20%)
- PDFs with high-res photos: Excellent compression potential (50-80%)
- Scanned documents: Usually compressible by 30-60%
- Already compressed PDFs: Minimal additional compression (5-15%)
If a PDF was already exported at low quality or has been compressed before, you won't see dramatic improvements. Compression can't create quality—it can only trade it for smaller size.
When Compression Isn't Enough
Sometimes even aggressive compression won't get a file small enough. Alternatives:
Cloud Storage Links
As mentioned earlier, Gmail automatically offers to upload large files to Google Drive. Outlook integrates with OneDrive. This is often the cleanest solution for truly large files.
File Transfer Services
Services like WeTransfer, Dropbox Transfer, or Firefox Send allow sending large files via a temporary download link. Good for one-time shares with external recipients.
ZIP Compression
For documents that don't compress well as PDFs (like text-heavy files), zipping them can sometimes achieve better results. Some email systems handle ZIP files better than large PDFs.