A PDF made from TIFF scans is large because each page is stored as a full-resolution image without lossy compression. A 300 DPI A4 colour scan holds about 8.7 million pixels per page, so a few pages can exceed email limits. You can shrink it by compressing the PDF, scanning at a lower resolution, scanning in greyscale or removing pages you do not need.
Here is why each option works and how much it typically helps.
On this page
Key takeaways
- File size comes from pixel count and colour depth, multiplied by the number of pages.
- Compressing the finished PDF is the fastest fix.
- 200 DPI and greyscale are enough for most text documents.
- Remove blank and duplicate pages before sending.
Steps shown in the video
- Click Choose TIFF Files and select your TIFF images
- Each file is listed with a preview and its size
- Click Convert to PDF
- Download one PDF with every image
Why is the PDF so large?
The TIFF to PDF converter embeds each TIFF page without lossy compression, so the PDF keeps every detail of the scan. That is ideal for quality but means the size depends on how the scan was made.
| Scan resolution | Pixels per A4 page |
|---|---|
| 150 DPI | about 1240 × 1754 (2.2 million) |
| 200 DPI | about 1654 × 2339 (3.9 million) |
| 300 DPI | about 2480 × 3508 (8.7 million) |
| 600 DPI | about 4961 × 7016 (34.8 million) |
Going from 300 to 600 DPI quadruples the pixel count, and colour pages carry three times the data of greyscale ones.
Fix 1: Compress the PDF
Run the finished PDF through Compress PDF. It re-encodes the page images with compression, which usually shrinks scanned documents dramatically while keeping text readable. Check one page at 100 percent zoom after compressing.
Fix 2: Scan at a sensible resolution
- 200 DPI is enough to read and print ordinary text documents.
- 300 DPI suits small print, and gives text recognition a good chance.
- 600 DPI is for photos, fine artwork and archives that need maximum detail.
Fix 3: Use greyscale or black and white
Most letters and forms do not need colour. Scanning in greyscale stores one value per pixel instead of three, and pure black and white is smaller still. Keep colour for documents where stamps, signatures or highlights must be visible in colour.
Fix 4: Send only the pages that matter
Scanners often pick up blank backs of pages. Delete them with Remove Pages, or send just the relevant section with Extract Pages. For the conversion itself, see how to convert TIFF to PDF.
Target sizes for common uses
| Destination | Typical limit | What to do |
|---|---|---|
| Email attachment | Often 20-25 MB total | Compress, or split into parts |
| Online forms and portals | Often 1-10 MB per file | Compress and send only required pages |
| Cloud sharing link | No practical limit | Keep full quality |
Limits vary by provider, so check the exact figure. Compressing first and trimming pages second usually gets even large scans under portal limits.
Large TIFF to PDF files: FAQ
Why is my PDF bigger than expected after converting TIFF?
The TIFF pages are embedded at full quality without lossy compression, so the PDF size reflects the scan resolution, colour mode and page count.
How do I make a scanned PDF smaller?
Compress the PDF, rescan at 200 to 300 DPI in greyscale, and remove pages you do not need.
What DPI should I scan documents at?
200 DPI for ordinary text, 300 DPI for small print or text recognition, 600 DPI only for detailed images.
Will compressing a scanned PDF make it unreadable?
Not at sensible settings. Check a page at 100 percent zoom after compressing.
Does greyscale really make a difference?
Yes. Greyscale stores one value per pixel instead of three for colour.
Small enough to send, sharp enough to read
A large scan PDF is a sign of high quality, not a fault. Compress it, choose sensible scan settings next time and trim the pages, and the document fits any inbox.
