To make a PDF smaller, start with a moderate compression setting, inspect the downloaded copy and compare its exact size with the receiving service's limit. Keep the original. A text-heavy PDF may already be compact, while scans and photo reports often contain images that can be reduced. There is no single percentage that every document can achieve without a visible change.
Check what is inside the document
Try selecting a line of text and zooming into a photograph. Selectable text usually comes from a digital document; an entire page that behaves like one picture is probably a scan. A scan can also contain an invisible OCR text layer, so these checks are clues rather than a complete diagnosis. Look for blank pages, repeated attachments and large photos before choosing a setting.
If you still have the source document, exporting it again can be more effective than compressing an existing PDF. Reduce unnecessarily large source images and choose an export setting suited to the destination. A portfolio needs different image detail from a receipt. Keep the source file as well as the exported PDF so you can revise the result later.
A compression workflow you can check
- Save a separate original and note its byte size and page count.
- Open Compress PDF and read the processing disclosure and current limits before selecting your document.
- Start with the recommended setting. Download the result rather than judging only the preview.
- Open the first, middle and final pages. Check small text, signatures, charts and any photographs that matter.
- Compare the new size with the upload limit. If necessary, test a stronger setting from the original and inspect it again.
A smaller download is useful only if the recipient can still use the document. Search for a name or reference number, copy a short text passage and compare the characters with the original. Page appearance and selectable-text fidelity are separate checks. Do not assume that a file which looks correct will preserve every form field, annotation or text encoding.
What our compression tests actually show
The published benchmark results include a text-heavy government PDF, a photo report and a colour scan, with original bytes, output bytes, settings and test conditions. The browser engine returned the already optimized text document unchanged. The photo and scan samples became smaller. Those are measured results for the listed files, not promised savings for every upload.
Browser and server processing can produce different results. The benchmark report separates their measurements and notes text differences found in a server-processed sample. Follow the disclosure on the tool page to understand the method used for your file. Processing time also depends on hardware and document complexity; a test-machine timing is not a completion deadline.
When a strict upload limit still cannot be met
Check whether the portal counts kilobytes using decimal or binary units and whether it applies a per-file or combined limit. Leave some room below the displayed maximum. If an application accepts separate attachments, split the PDF into the required sections. If it needs only selected pages, remove irrelevant material before another compression attempt. Follow the submission instructions rather than changing required page content.
OCR makes recognized text searchable; it does not by itself guarantee a smaller file or perfect recognition. Rasterizing a whole document can reduce some kinds of content but can also remove selectable text and soften small print. Avoid converting an important digital document into page images just to chase a smaller number. A signed document should be checked carefully because modification can affect signature validity.
Before you send the result
Confirm page order, final byte size, readable text and the receiving service's requirements. Open the saved file in another viewer if possible. For forms, test the fields you need; for scans, inspect fine print and stamps. If the result loses information, return to the original and use a gentler setting, a new export or an allowed split. Keep both versions until the submission is accepted.