Two PDFs can look almost identical on screen and behave completely differently. In one, you can select and search individual words. In the other, the whole page behaves like a single image. The reason is often simple: one file contains real text objects, while the other is a scan.
What is a text-based PDF?
In a text-based PDF, letters and words are stored as text objects. These files are commonly created by exporting from a word processor or another digital document system.
Typical signs are that you can select, copy, and search text. Editing is also more likely to be possible, although actual editability still depends on the PDF's internal structure.
What is a scanned PDF?
A scan starts as an image of a page. To a computer, the printed sentence is initially just a pattern of pixels, not automatically text. That is why the PDF can look perfectly readable while individual words cannot be selected.
Three quick tests
- Select: Try selecting a single word. A pure scan usually will not let you.
- Search: Search for a clearly visible word. No result can indicate that there is no usable text layer.
- Copy: Paste a sentence into a text editor. If nothing useful appears, inspect the document more closely.
OCR does not magically turn a scan into a perfect text PDF
Optical character recognition identifies characters in an image and can add a searchable text layer. Search and copy-and-paste then become possible even though the visible page may still be an image.
OCR can make mistakes. Low-quality scans, unusual fonts, tables, handwriting, and poor resolution can all reduce accuracy.
Why the distinction matters for editing
Editing existing PDF text is different from changing text inside an image. A PDF editor can address text objects in a digital PDF. A scan may contain only image data at that location.
Priviot PDF can edit existing PDF text, but editability depends on the internal structure of the file. A scan with no corresponding text objects is therefore a different case from a digitally generated document.
Why the distinction matters for redaction
After OCR, a scanned document can contain both visible image content and an invisible text layer. If you redact sensitive information, you need to consider more than the pixels you can see.
Priviot's redaction function is designed to remove selected content from supported document structures and only rasterize complex pages after consent. You should still review the saved result.
Which type is better?
It depends on the purpose. Text PDFs are generally better for search, copy-and-paste, and often accessibility. Scans are useful when the source exists only on paper or when the exact appearance of a physical original needs to be preserved.
Many archival workflows combine both: a visible scan with an OCR text layer underneath.
Conclusion
The simplest distinction is this: text PDFs contain real text objects; pure scans initially contain images. Selection, search, and copy tests quickly reveal the difference. OCR can make scans searchable, but it does not automatically change every aspect of the PDF's structure.