How to Reduce a PDF's File Size
Why PDFs get huge and five ways to shrink them for email and upload limits: compression, grayscale, splitting, removing pages and more.
Most email services cap attachments at 20-25MB, and upload portals often allow only 2-5MB. Here's why PDFs get so big and what actually helps.
Why is my PDF so large?
Almost always it's images. A scanned page saved at 600 DPI in colour can be 5-10MB on its own. Text-only PDFs are rarely more than a few hundred KB, even with hundreds of pages.
1. Compress the images
Compress PDF re-renders each page at a sensible resolution with efficient JPEG compression. For scans, 120 DPI is perfectly readable on screen and typically 70-90% smaller. The trade-off: text in the compressed copy can no longer be selected.
2. Go grayscale
If colour doesn't matter, convert to grayscale. Many courts, universities and offices prefer black and white anyway.
3. Remove pages nobody needs
Blank pages, duplicate scans and cover sheets add weight. Delete them before compressing.
4. Split it
If a portal has a strict per-file limit, split the PDF into parts and upload them separately.
5. Scan smarter next time
Scan documents at 150-200 DPI in grayscale. That's sharp enough for printing and OCR and keeps each page around 100-300KB.
How to compress a PDF to under 1MB
Choose the "Strong" or "Maximum" level in Compress PDF. For long scanned documents, combine it with grayscale and remove unneeded pages. If it's still too big, split it.