Searchable PDF & compression

When you process a document, Scanix Desktop's default output is a Searchable PDF — a file that looks exactly like your scan but is fully findable and copyable. This page explains what that format actually is, why it stays faithful to the original, and how the optional high-compression mode makes those files dramatically smaller for high-volume archives. For the step-by-step of exporting, see Export formats.

What a Searchable PDF really is

A Searchable PDF is two things stacked on top of each other: the page image you scanned, and an invisible, selectable text layer laid precisely over it. The picture is what you see; the hidden text is what your PDF reader searches, selects, and copies. Because the text sits behind the image rather than redrawing the page, the document looks pixel-for-pixel identical to the scan — but anyone can now find a phrase in it, highlight a value, or copy a paragraph out, using nothing more than an ordinary PDF viewer.

That invisible layer is built directly from OCR. So the rule is simple: a page that has been read by OCR carries selectable text; a page that was never OCR'd is embedded as an image only. The image-only page still appears in the PDF and prints fine — it just has nothing to search or copy, because no text was ever recognized for it. If searchability matters for every page, make sure each one is read before you export.

Corrections you make to the recognized text flow straight into this layer, so fixing a misread word in the viewer is a fix that everyone searching the final file benefits from. The text layer is yours to refine right up until export.

High-compression (MRC) output, and why it exists

A plain Searchable PDF keeps each page at full resolution, which is exactly what you want for fidelity but can make large archives heavy on disk. High-compression output, also called MRC (mixed raster content), is an optional mode that shrinks those files substantially while keeping text crisp. The idea behind MRC is to treat a page as layers — sharp text separated from the smoother colour background — and compress each in the way that suits it, rather than squashing the whole page uniformly. The result is a much smaller searchable PDF that still reads cleanly.

It is a deliberate trade-off between file size and image fidelity, so Scanix keeps it off by default and lets you pick how aggressive it should be. It applies only to Searchable PDF output; other export formats are unaffected.

Choosing a compression level

Once the master switch is on, a Compression level choice appears wherever Searchable PDF output is configured, with these presets — from no compression at all to fully lossless archival:

The mental model runs in one direction: higher level, smaller file, less margin for image fidelity. High (recommended) is the sweet spot for ordinary office documents — invoices, correspondence, contracts — where you want a small file and sharp, readable text. Reach past it to Extra High only when raw file size is the priority and you can accept softer photos or shaded backgrounds. Step back to Archival — lossless text when the document is an original of record and you cannot afford to lose any image detail.

Where you set it at export

Because the level lives with the Searchable PDF output, you can set it in two natural places, depending on whether you want it baked into a repeatable job or chosen for one export:

In both places it's the same set of presets, and the choice only takes effect for Searchable PDF output with a level other than Off — no compression. If you switch the output to a non-PDF format, the compression control simply doesn't apply.

Frequently asked

Next steps

Related

• Export formats
• OCR overview
• General settings