BASALT · JOURNAL
Why you cannot select text in a PDF
Three different problems produce the same symptom, and the fix is different for each.
One: it is a scan
The most common by far. The page is a photograph, so there is no text to select. Your cursor draws a rectangle instead of highlighting.
Confirm with pdftotext document.pdf - | head. Empty output means no text layer.
The fix is OCR, which adds an invisible text layer over the image. On macOS this runs on device.
Two: the text is there but does not map to characters
Less common and more confusing. Selection works, copying produces gibberish or nothing.
This happens when the font is subset and lacks a reverse mapping from glyph codes back to Unicode. The document renders perfectly because the glyphs are present, but nothing tells the reader which characters they represent.
There is no clean fix. OCR over the rendered page is the practical workaround, because it reads the picture rather than the encoding.
This one is worth knowing for a second reason: it means copy and paste is a poor test of whether a document has been redacted. A file can hold the original text perfectly well while pasting nothing readable.
Three: selection is disabled
The document has permissions set that forbid copying. Most viewers honour this.
It is a request rather than a protection. The text is present and readily extractable by tools that ignore the flag, so treat it as a courtesy setting and never as security. If the content genuinely must not be copied, it should not be in the document.
Telling them apart quickly
Try pdftotext. Nothing at all means a scan. Gibberish means a font mapping problem. Correct text despite the viewer refusing to select means a permissions flag.
That single command distinguishes all three in a second.
Frequently asked questions
Why can I not select text in my PDF?
Usually because the page is a scanned image with no text layer. Less commonly the fonts lack a reverse mapping to Unicode, so text renders but copies as gibberish, or the document has a permissions flag that asks viewers to forbid copying.
How do I tell if a PDF is scanned or just protected?
Run pdftotext document.pdf - and look at the output. Nothing at all indicates a scan, gibberish indicates a font encoding problem, and correct text indicates a permissions flag your viewer is honouring.
Can I copy text from a PDF that blocks copying?
Usually yes, because the flag is a request that cooperative viewers honour rather than a protection. The text remains in the file and is extractable by tools that ignore it, which is why it should never be relied on for confidentiality.
Why does copied PDF text come out as gibberish?
The fonts are subset without a mapping from glyph codes back to Unicode characters. The page renders correctly because the shapes are present, but nothing records which characters they are. OCR over the rendered page is the practical workaround.
Doing it in Basalt
Basalt is a native macOS PDF toolkit: eighteen tools in one window covering merge, split, page organisation, compression, OCR, passwords, Bates numbering, forms, signing, watermarks and comparison. Every file is processed on your Mac, and the engine that opens documents holds no network entitlement at all, which macOS enforces at the code-signature level. Redaction destroys content rather than covering it, and an independent verifier proves the material is gone before a file is written. A one time $29 licence covers up to three Macs, free for the first 24 hours. Get it at basaltformac.com, or brew install --cask chipmunk1101/tap/basalt.
Redaction that proves itself
Basalt destroys the content you mark, then re-opens the file it wrote and proves the content is gone before it saves anything. Your documents never leave your Mac.