Check file size (25MB max) and page count (20) before uploading; long documents silently lose data past page 20. Send one document per API call, not batches. Strip tiny attachments like signature icons under 5KB or they vanish without an error. Use png, jpeg, jpg, pdf, tiff, or tif only.

Context: Official docs (Docsumo upload limits): documents hard upload limits: 25MB max per file, 20 pages per document (documents with more pages are still processed but extraction only runs on the first 20, and those same pages go to the review queue), one document per API call, and attachments smaller than 5KB are silently skipped. Common upload failures include files too small, more than 100 documents in an email, and invalid file types.