BASALT · JOURNAL
Exporting PDF pages as images
Exporting a page as an image is straightforward. The decisions are resolution and format, and both matter more than people expect.
In Preview
File, Export, then choose PNG or JPEG and set the resolution. Preview exports the current page only, so a multi page document needs each page done separately, which is why people look for another route.
Resolution
72 DPI is screen resolution and looks poor when printed or zoomed. 150 DPI is adequate for on screen use at full size. 300 DPI matches print quality and is the sensible default if the image will be read rather than glanced at.
Higher than 300 rarely helps for text and multiplies file size quadratically.
PNG or JPEG
PNG is lossless and handles sharp edges cleanly, which is what text is. Larger files, but no artefacts around characters.
JPEG is smaller and blurs sharp edges, producing halos around text. Fine for photographs, poor for documents.
For a page of text, PNG. For a page that is mostly a photograph, JPEG.
What you lose
Everything except appearance. The text becomes pixels, so the result is not searchable, not selectable, and not accessible to a screen reader.
That is sometimes exactly what you want, and it is worth being deliberate about it rather than discovering it later.
The one case where this is a redaction technique
Rendering a page to an image and rebuilding the PDF from that image destroys everything that was not visible: hidden layers, text under boxes, form values, the lot.
It is heavy handed, it makes the document unsearchable, and it is the fallback when a page cannot be processed any other way. Used deliberately it is sound. Used accidentally it produces a document nobody can search and everybody assumes is still text.
Frequently asked questions
How do I convert a PDF page to PNG on Mac?
In Preview, use File then Export and choose PNG with a resolution. Preview exports one page at a time, so multi page documents need a tool that handles the whole file.
What resolution should I export PDF pages at?
300 DPI for anything that will be read or printed, 150 for on screen use at full size. Above 300 rarely improves text and multiplies file size quadratically.
Should I export pages as PNG or JPEG?
PNG for pages of text, because it is lossless and keeps sharp character edges clean. JPEG for pages that are mostly photographs, where its compression suits the content and the file is much smaller.
Does converting a PDF page to an image remove hidden content?
Yes. Rendering to an image and rebuilding from that discards everything not visible, including hidden layers and text under boxes. It also makes the page unsearchable, so it is a deliberate fallback rather than a default.
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. 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.