PDF compression guide
Half the battle with PDF size is knowing the number you are aiming for. Limits vary widely - generous for email, often strict for government and application portals - and they change over time, so the golden rule is to read the limit shown on the page in front of you and treat any general figure, including the ones here, as a starting point rather than gospel.
Most consumer email services allow attachments in the region of 20-25 MB, and when a file exceeds that they typically offer to send a cloud link instead. Because exact limits change and differ between providers, check your provider's current help page when it matters. The catch that catches people out is the receiving side: even if your provider accepts a file, the recipient's mail system may reject anything above its own, often stricter, threshold.
A PDF that leaves your outbox can still bounce before it lands, because it has to satisfy the smallest limit anywhere along the way. If you do not know the recipient's limit, aim comfortably under the common 20-25 MB range. For anything large or important, a 1MB or 2MB compressed PDF is a safe, fast-loading choice that avoids borderline rejections entirely.
Where email is roomy, upload forms are often tight. Visa, immigration, examination, banking and job-application portals frequently cap individual documents at a few hundred kilobytes, and sometimes at 100 KB. They also tend to enforce format and clarity rules and to reject a file outright if it breaks them. These are exactly the cases where target-based compression earns its keep - and where you should read the portal's instructions before you compress.
Work from the limit downwards. If a form allows 2 MB, start at the 2MB target and only step down if you must. If it caps you at 500 KB, our testing shows that target keeps most documents sharp. Reserve 200KB and 100KB for forms that genuinely demand them, because that is where scanned detail starts to soften. Matching the limit rather than beating it is the single biggest thing you can do to protect quality.
As a rough guide: for email, keep PDFs under about 20 MB and prefer 1-2 MB for smooth delivery; for general upload forms, 500 KB is a safe, high-quality default; for strict application portals, follow the stated cap exactly, which may mean 200 KB or 100 KB. Always confirm the real figure on the page, then choose the largest target that fits.
Most email services allow roughly 20-25 MB, but limits change and the recipient's server may be stricter. Check your provider's current help page, and compress large files to 1-2 MB to be safe.
Many were built around small attachments and process huge volumes of documents, so they cap uploads tightly - often a few hundred KB, sometimes 100 KB - to keep storage and bandwidth manageable.
When in doubt, 500 KB is a safe, widely accepted default that keeps most documents readable. Only go smaller if a form specifically requires it.