BASALT · JOURNAL
The location data hiding in your PDF's images
A photograph taken on a phone records where it was taken. When that photograph is placed into a PDF, the embedded image can carry that data with it.
This is one of the least known disclosure routes in document work and one of the most consequential, because a precise location is exactly the information some people most need to protect.
Why standard checks miss it
Document metadata and image metadata are different things in different places.
exiftool on the PDF reads the document information dictionary and XMP packet: title, author, producer, dates. Stripping those does not touch data inside an embedded image stream.
A reviewer looking at the visible page sees nothing at all, because none of this renders.
When it matters
Family matters where an address must not be disclosed. Journalism where a photograph's location identifies a source or a site. Insurance and investigation files containing photographs taken at someone's home. Any document where a picture was taken somewhere that should stay private.
Reducing the risk
Strip metadata from images before placing them into documents. Most image editors do this on export, and exiftool -all= removes it from a file directly.
Where a document already exists, extracting its images and inspecting them is the only way to be certain:
pdfimages -all document.pdf outdir/prefix
exiftool -gps:all outdir/*That extracts every embedded image and reports any GPS data.
The general principle
The file contains more than the page displays. Metadata, attachments, earlier revisions, form values, OCR text and embedded image data are all instances of the same thing.
Checking what a page shows tells you about the page. Only checking the file tells you about the file.
Frequently asked questions
Can a PDF reveal where a photo was taken?
Yes. An embedded photograph can carry EXIF metadata including GPS coordinates, and nothing on the visible page reveals it. Stripping the PDF's own metadata does not remove data inside image streams.
Does removing PDF metadata remove image metadata?
No. They are separate. Document metadata is the information dictionary and XMP packet; image metadata lives inside the embedded image stream and survives a document level strip.
How do I check images in a PDF for location data?
Extract them with pdfimages -all document.pdf outdir/prefix, then run exiftool -gps:all over the extracted files to report any GPS data.
How do I remove metadata from images before using them?
Most image editors strip it on export, and exiftool -all= removes it from a file directly. Doing this before placing photographs into a document is more reliable than trying to clean it afterwards.
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.