The document workshop / Limits

Compress a PDF to a Specific Size

Targeting 5MB, 10MB or 25MB? Here's how the numbered modes work — and why they're best-effort.

Sometimes the constraint is a hard number on an upload form. Under 5MB, Under 10MB and Under 25MB mean strictly less than 5,000,000, 10,000,000 and 25,000,000 bytes respectively. A file exactly on the threshold does not satisfy the mode. If the validated original is already under it and no other transformation is requested, the original is kept byte for byte.

The honest framing matters here. These are best-effort targets, not promises. A short, image-light PDF slips under easily; a long, detailed, or already-compressed one can hit the mode's quality floor before it reaches a small target. When that happens, the right answer is usually to split the file at a natural break, not to crush it further and ruin every page.

The modes test candidates over a limited number of passes. Among candidates that fit, the engine prefers colour, effective resolution and JPEG quality parameters; if none fits, it chooses the smallest candidate. These parameters are not a measured visual-quality score. Under 5MB and Under 10MB may use grayscale, while Under 25MB uses colour. Read target attainment separately from the size reduction.

Match the mode to the task.

Targets are best effort. The final size and warnings are shown with your result.

Choose an approach
Your situation	Mode	What to expect
Under 25MB (common personal-email cap)	Under 25MB	Highest starting resolution and JPEG quality among numbered modes, in colour. Inspect the output; file size alone does not rank quality.
Under 10MB (typical portal or upload cap)	Under 10MB	A best-effort 10MB target for a destination that explicitly accepts it; may use grayscale.
Under 5MB (strict forms)	Under 5MB	Works hardest across several passes; expect visibly softer images at this target.
Already small, just needs a trim	Email	If you're only just over the line, one balanced pass may be enough — no need for an aggressive target.
Big scan that won't reach the number	Scanned	Grayscale may reduce a monochrome scan, but this mode has no numeric target. Check its size and preserve meaningful colour with another mode.

Articles & resources.

Read further before choosing your settings.

No specific articles published for this topic yet.

Frequently Asked Questions

Can the tool promise my file lands under the limit?

No. A result can be smaller and still miss the target. Split with a separate editor only if the destination accepts parts, or use another approved delivery method.

What if it won't get small enough?

Split the PDF at a natural break and send it in parts, re-scan a bloated scan at a lower resolution, or share a link instead of attaching. Each beats forcing a file below its floor.

Why did my file barely shrink?

An original already under a numbered target is kept unchanged. In normal compression, a candidate without a saving also keeps the original. Remove metadata supplies the cleaned output even if it grows, with a warning.

Put the advice to work.

Mode: Email. Review the result before sharing your file.

Start compressing