BASALT · JOURNAL
Cropping PDF pages on a Mac
Cropping a PDF does not remove anything. It sets a box that tells viewers which part of the page to display, and everything outside it remains in the file.
That is worth knowing before you use cropping to hide something.
How to crop
In Preview: select the area with the rectangular selection tool, then Tools, Crop, or press Command K.
The result displays as the cropped region, and the material outside is still present.
Why it is not removal
A PDF page has several boxes. The MediaBox is the full page and the CropBox is the visible region. Cropping usually adjusts the CropBox, so the content beyond it is merely not drawn.
Anyone can restore it by resetting the box, which is a single operation in many tools. Text outside the crop is also still extractable, so a search of the document finds it.
When this matters
If you cropped to remove a header containing a client name, a margin note, or part of a scanned page showing something that should not be shared, the information is still in the document.
The test is the same as for any other concealment: extract the text and search it.
pdftotext cropped.pdf - | grep -i "whatever you hid"If it appears, the crop hid it visually and nothing more.
Cropping content away properly
To genuinely remove material outside a region you need either a redaction that destroys the content, or a re-render of the page as an image at the cropped size, which discards everything else but also discards the text layer and makes the page unsearchable.
For scanned pages the second is sometimes acceptable. For text documents it is usually the wrong trade, and a proper redaction is the right tool.
A legitimate use
Cropping is entirely appropriate for presentation: removing scanner edges, tightening margins for reading on a small screen, or trimming whitespace before printing. The trouble only starts when it is used as a privacy measure.
Frequently asked questions
How do I crop a PDF on Mac?
In Preview, select the area with the rectangular selection tool and press Command K, or use Tools then Crop. The document then displays as the cropped region.
Does cropping a PDF remove the content outside the crop?
No. Cropping adjusts a box that tells viewers what to display, and the content outside remains in the file. It can be restored by resetting the box, and text outside the crop is still extractable.
Can cropped PDF content be recovered?
Yes, easily. Resetting the crop box is a single operation in many tools, and any text beyond the crop is found by ordinary text extraction.
How do I actually remove content outside a crop?
Use a redaction that destroys the content, or re-render the page as an image at the cropped size. The second removes everything else but also removes the text layer, so the page is no longer searchable.
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.