Why Is My PDF So Large? Causes & Fixes — Free Online Guide
· How-To · 6 min read
A 2-page document shouldn't be 40MB. Here's the real reason PDFs get bloated and the specific steps to fix each cause.
A two-page document that's 40MB is not normal. But it's more common than it should be, and the causes are almost always fixable. Here's what's making your PDF large and what to do about each cause.
Common Causes at a Glance
Cause
How Common
Typical Size Contribution
Fix
High-resolution embedded imagesVery common5–15 MB per imageCompress PDF
Scanned pages at high DPIVery common1–3 MB per pageCompress PDF
Redundant metadataCommon500 KB – 2 MBStrip metadata
Full font embeddingOccasional1–5 MBCompress or re-export
Wrong export applicationOccasional10–30 MBRe-export properly
Cause 1: High-Resolution Images
This is responsible for the majority of oversized PDFs. When you insert an image into Word and save as PDF, the image is embedded at its original resolution. A photo from a modern smartphone is typically 12–48 megapixels. A single full-resolution smartphone photo can add 5–15MB to a PDF. A document with 5 photos becomes enormous.
Fix: Use our PDF compressor and select Medium compression. A 35MB document with embedded photos routinely comes down to 2–4MB with no visible quality difference on screen.
Cause 2: Scanned Documents
Scanned PDFs are essentially stacks of images. Each page is a raster image stored inside the PDF container. Scanner default settings are often 300–600 DPI, which produces high-quality images — and large file sizes.
10 pages at 300 DPI → typically 3–10 MB
10 pages at 600 DPI → typically 6–20 MB
Fix: For scanned documents you're sharing digitally (not archiving), compressing to 150 DPI screen quality reduces file size by 60–80% with no visible difference at normal reading size.
Cause 3: Embedded Fonts
PDFs embed fonts to ensure the document looks the same on every device. Most of the time, only the characters actually used are embedded (font subsetting), which keeps the size small. But some applications or settings embed the entire font file — including all characters you didn't use.
A document with several embedded custom fonts can accumulate 1–5MB in font data alone. This is less common than image bloat but worth knowing about for text-heavy documents that are still surprisingly large.
Cause 4: Metadata and Hidden Data
PDFs from Word often contain metadata you don't need for sharing:
Full revision history and edit timeline
Author name, company, and software version
Embedded high-resolution thumbnail previews
Color profiles and printer settings
Stripping this metadata is one of the lossless optimization passes our compressor applies — no visible change, meaningful reduction in file size.
Cause 5: Wrong Export Application
Different applications produce PDFs of vastly different sizes from identical source content:
PowerPoint "Save as PDF" on Windows — often 5–10× larger than it needs to be
macOS "Print → Save as PDF" — usually much more efficient
macOS "File → Export as PDF" — typically the cleanest output
Microsoft Print to PDF on Windows — more efficient than PowerPoint's native export
Normal File Size Reference
Document Type
Pages
Normal Size
Investigate If Over
Text-only document10 pages100–500 KB1 MB
Mixed text and images10 pages1–5 MB10 MB
Photo-heavy document10 pages5–15 MB30 MB
Scanned document (300 DPI)10 pages3–10 MB20 MB
Presentation (exported)20 slides2–8 MB20 MB
Anything significantly over the "investigate" column for a standard business document should be compressible — start with our PDF compressor and work from there.