Compress PDF for LMS Upload — Canvas, Blackboard & Moodle Size Limits
Fit assignment PDFs under Canvas, Blackboard, and Moodle caps. Compression levels, scan settings, and platform limit reference.
Published June 1, 2025 · 2 min read
3 uses per day · 200 MB · TLS encrypted · auto-delete
LMS PDF upload limits — Canvas, Blackboard, Moodle
Learning management systems cap assignment uploads at the institution level and sometimes per-assignment. Typical defaults:
| Platform | Instance default | Safe target |
|---|---|---|
| Canvas | Up to 100 MB per file | Check assignment page — instructors may set 10–25 MB |
| Blackboard Learn | 50–250 MB (admin-configured) | Under 10 MB for compatibility |
| Moodle | 50–200 MB (site setting) | Under 10–25 MB unless assignment specifies otherwise |
Full table: attachment size limits. Tool: Compress PDF. Pillar links Canvas and Blackboard here (merged P0 URLs).
Why students hit LMS upload errors
- Instructor lowered cap — assignment says 10 MB but Canvas instance allows 100 MB.
- Phone photo of handwritten homework — 300 dpi colour photos exceed caps quickly.
- Combined report + appendix — merged PDF from multiple scans without compression.
- Slow campus Wi-Fi timeout — large files fail mid-upload; smaller files succeed.
Step-by-step: compress PDF for LMS submission
- Read the assignment page for the exact file size limit and accepted formats (PDF only vs PDF/DOCX).
- If scanning homework, use document mode at 200–300 dpi grayscale before PDF export.
- Upload to Compress PDF → Recommended for typed reports; Less for handwritten scans where clarity matters.
- Verify equations, handwriting, and diagrams at 100% zoom.
- Submit on Canvas/Blackboard/Moodle before the deadline — keep a local copy.
Student merge workflow: merge PDF for students · compress PDF for students.
Platform-specific notes
Canvas
Many U.S. universities run Canvas with generous instance limits, but professors routinely set 5–20 MB on final papers. Check the rubric. Mobile Canvas app uploads fail more often on large files — compress before submit.
Blackboard
Older Blackboard instances at community colleges often cap at 10 MB. Target 8 MB after compression for safety. Safe Assign and Turnitin still accept compressed PDFs if text is selectable.
Moodle
European and APAC institutions on Moodle — limits vary widely. If upload fails silently, compress to under 5 MB and retry.
Typed report vs handwritten scan
- Word/Google Docs export — often under cap already; compress only if over limit or for faster upload.
- Handwritten math/science — use Less compression to preserve pencil marks; re-scan at lower DPI instead of Extreme.
- Group project merge — merge sections, then one Recommended compression pass. Compress before or after merge.
Faculty and TA distribution
Instructors uploading reading packs to LMS:
- Compress scan-heavy readings before posting — students on mobile data benefit.
- Compress PDF for teachers
- OCR scanned chapters for searchable course packs: OCR PDF
Troubleshooting
- Upload stuck at 99% — file too large for assignment cap; compress and retry.
- Turnitin similarity report missing — usually unrelated to compression if text layer exists.
- Professor cannot open your PDF — avoid password protection; export standard PDF from Word.
Related guides
- Email (submitting to professor via email instead)
- Common App · University application
- Compress PDF guide
3 uses per day · 200 MB · TLS encrypted · auto-delete
Frequently asked questions
What is the PDF size limit for Canvas uploads?
Canvas often allows 100 MB per file on many instances — but instructors may set lower caps; check the assignment page.
How do I compress a PDF for Blackboard?
Blackboard commonly limits uploads to 10–25 MB depending on admin settings — compress to under 10 MB for safety.
Will compression blur scanned homework?
Use Recommended for typed PDFs; Less for handwritten scan submissions.
Sources & references
Primary references used when researching and fact-checking this guide. See our editorial methodology.
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Ghostscript documentation — PDF settings
— Artifex Software
Compression level behavior and PDF output settings.