You have finished your document, converted it to PDF, and are ready to send — only to discover the file is 28 MB and your email client has a 25 MB attachment limit. Or perhaps the online portal you are submitting to rejects anything over 5 MB. Reducing file size is one of the most practically useful document skills you can have. This guide covers the most effective techniques for PDFs, Word documents, and images.
Why Files Are Larger Than They Need to Be
Most oversized documents share a few common causes:
- High-resolution images. A single uncompressed photo can be 10–20 MB. Embedded in a document, multiple photos quickly create enormous file sizes.
- Embedded fonts. Some PDFs embed entire font files, which can add several MB.
- Revision history and metadata. Word documents accumulate editing history, author information, and other hidden data that inflates file size.
- Redundant data. PDFs can contain duplicate objects, unused resources, and inefficiently structured data that compression can eliminate.
- Scanned pages. Scanned PDFs are essentially images — one scanned page can be several MB depending on the scanner resolution.
Reducing PDF File Size
Use a PDF Compressor
The simplest approach. Toolzilla's PDF Compressor uses object stream optimisation to reorganise the internal structure of the PDF, eliminating redundant data. This is most effective on PDFs with embedded images, but provides some reduction on all file types.
Reduce Image Resolution Before Creating the PDF
If your document contains photographs, reduce their resolution before converting to PDF. For screen viewing and email, 96–150 DPI is more than sufficient. For print, 300 DPI is standard. Anything above 300 DPI in a document intended for email or digital submission is wasted data.
For Scanned Documents, Adjust Scanner Settings
If you are scanning physical documents, set your scanner resolution to 150–200 DPI for text documents. 300 DPI is appropriate only if you need to read very small print. Higher resolutions produce dramatically larger files with minimal visible improvement.
Reducing Word Document File Size
Compress Images Inside Word
Click any image in your document → select Format → Compress Pictures → choose "Email (96 ppi)" or "Web (150 ppi)." This reduces the resolution of all embedded images and typically achieves 50–80% size reduction in image-heavy documents.
Accept All Track Changes
Word stores the full text of every tracked change in the file. A document with extensive revision history can be significantly larger than the same document with all changes accepted. Go to Review → Accept → Accept All Changes before saving.
Remove Hidden Metadata and Personal Information
Word stores author information, editing time, and revision history as hidden data. Go to File → Info → Check for Issues → Inspect Document and remove hidden data before sharing.
Save as .docx Not .doc
The older .doc format is consistently larger than the modern .docx format. If you are working with a .doc file, save it as .docx — the difference can be substantial, often 30–50% smaller.
Reducing Image File Size
- Use JPG for photos. JPG compression is specifically designed for photographic images and produces small file sizes with good quality.
- Use PNG for screenshots and diagrams. PNG uses lossless compression — ideal for images with text, sharp lines, and solid colours where JPG artefacts would be visible.
- Use WebP for web delivery. WebP produces files 25–35% smaller than equivalent JPGs at the same quality — excellent for web images.
- Resize before sharing. A 4000 × 3000 pixel photo is unnecessarily large for email or documents. Resize to the actual display size needed.
File Size Limits for Common Platforms
- Gmail: 25 MB per email
- Outlook: 20–25 MB depending on organisation settings
- WhatsApp: 100 MB for documents
- LinkedIn: 100 MB for uploaded documents
- Government portals: Typically 5–10 MB — always check the specific limit
- Job application portals: Typically 2–5 MB — compress your resume PDF
When in doubt, aim for under 5 MB for any document you plan to submit or email. This covers virtually every platform limit and keeps download times fast for recipients on slow connections.