How to reduce the size of a scanned PDF

What this workflow helps you do

A scanned PDF normally contains page images rather than ordinary selectable text. This workflow explains where Compress PDF fits and when OCR or a separate image step is required.

Compress scanned or photo-heavy pages where image quality can be traded carefully for a smaller document.

Plan the task in Compress PDF

Reduce PDF file size in your browser, choose an appropriate compression level, and review the size-versus-quality result before downloading the new copy.

PDFKaka first offers structure-preserving compression for documents where selectable text and interactive features matter. Stronger image-based modes are available for scanned or image-heavy files, but no mode promises an exact final size. The result depends on page count, dimensions, colours, and source content.

1. Start with structure-preserving compression. Recommended compression safely rewrites the document structure without intentionally turning every page into an image. It publishes a result only when the output is meaningfully smaller.
2. Use stronger compression for image-heavy files. Strong and Maximum modes render pages as compressed images. They can reduce scans more substantially, but fine print, signatures, diagrams, and identification details may become harder to read.
3. Understand what compression changes. Recommended mode keeps selectable text and document features where possible. Stronger image-based modes do not retain selectable text, links, forms, accessibility data, or signatures, so keep the original PDF.

Identify image-only pages before choosing the next step

A scan can look like an ordinary PDF while storing each page as one image. Compress PDF may still handle the page visually, but text search, extraction, editing, and exact-text operations need real text objects or a reviewed OCR layer.

Try selecting a sentence in a reader. If the whole page behaves like one image, plan for OCR where supported and expect to verify recognition errors manually.

1. Check whether text is selectable on several pages.
2. Inspect scan focus, contrast, skew, shadows, and cropped edges.
3. Verify OCR names, dates, numbers, and reading order when OCR is used.

Settings and limitations to check

Can PDFKaka compress a PDF to exactly 100KB? Standard compression reduces file size but does not guarantee an exact final byte size. Check the downloaded result against the upload limit.

Why did my text-only PDF not become much smaller? Digitally created text PDFs can already be compact. Recommended compression will not publish a larger or negligibly smaller copy just to claim success.

Are my PDF files uploaded to a server? No. Compression is processed in your browser.

1. Use only the settings needed for the required result.
2. Keep the source file available for comparison.
3. Do not rely on an unsupported exact-size, fidelity, or security promise.

Review the completed file

Verify that page images remain readable and remember that searchable text, links, forms, and signatures are not preserved by raster rebuilding.

Open the downloaded result in a separate viewer, inspect important pages or details, and repeat the workflow with adjusted settings if the output is not suitable.

1. Confirm the expected file type and page count.
2. Check important text, images, order, and orientation.
3. Share or submit only the reviewed copy.