Recommended or Smallest File: Picking a PDF Compression Preset for an Upload Limit

Compress PDF offers exactly two presets, on purpose - not a dozen sliders, because most people reaching for a PDF compressor have one real question: does this get small enough to clear a specific limit, or not. Here's what actually separates Recommended from Smallest file, and how to decide.

Recommended: the default for a reason

Recommended re-encodes embedded images at a quality level chosen to keep pages looking the same at normal viewing size - reading on a screen, printing at standard size, the kind of everyday use most PDFs actually get. In testing, a typical scanned document came down about 45% smaller at this setting. It's the right choice whenever there's no hard size ceiling to hit and the goal is simply "smaller without a visible tradeoff."

Smallest file: for when there's a number to beat

Smallest file goes further on two fronts at once: a lower JPEG quality, and capping any oversized embedded image down to a 1600px long edge before re-encoding. In testing, a typical scan came down around 75% smaller at this setting - a meaningfully bigger cut than Recommended, at the cost of some sharpness that's genuinely only visible if you zoom in close on the final result. This is the setting worth reaching for when there's an actual limit standing in the way: an email attachment cap, a web form's upload ceiling, a portal that silently rejects anything over a certain size.

What neither preset changes

Both presets only touch embedded JPEG images. Neither one resizes the page itself, removes pages, changes text, or lowers any resolution beyond the images captured inside the file - the document's actual layout and content are identical either way, just the weight of the photos inside it. A very large image is also capped at a 4000px long edge no matter which preset is picked - a memory guard for a phone browser processing a huge scan, not a quality choice either preset makes for you.

If Smallest file still isn't small enough

A document that's already mostly text with a small number of embedded images has a hard ceiling on how much either preset can save, because there's a limited amount of image data to shrink in the first place. If a strict size limit still isn't cleared after Smallest file, the honest options are splitting the document into smaller pieces, or accepting that the images in it need to stay near their current quality for the document to remain legible - not a setting this tool, or any image compressor, can invent around.

Running it twice is safe, not a way to compound savings

Compressing an already-compressed file doesn't stack a second round of savings on top of the first - the tool checks whether recompressing would actually help, and when it wouldn't, it returns the file unchanged rather than degrading it further for no real gain. There's no benefit to running Smallest file after Recommended already ran; picking Smallest file from the start on the original scan gets to the same result in one step.

Deciding without knowing the exact limit

Not every situation comes with a stated number - "the upload keeps failing" doesn't always come with the portal's actual size cap printed anywhere visible. When the limit is unknown, Smallest file is the safer starting point precisely because it's reversible in spirit even though the tool itself doesn't do multi-step comparisons: run the original through Smallest file first, since it gives the best chance of clearing a limit you can't see; if the result is far under any plausible limit, Recommended may clear it too, at better quality. Going the other direction - hitting a wall with Recommended, then re-running Smallest file on the same original - costs one extra pass but never any quality lost twice over, since each preset always starts fresh from the original file, not from the previous preset's already-compressed output.

Where this fits

Compress PDF offers both presets with one click each, entirely in your browser. The background covers why scanned PDFs get this large, and the how-to guide walks through the actual steps.