PDF metadata (www.pdf-tools.com) flags PDFs as modified?

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Level 2

291 points

PDF metadata (www.pdf-tools.com) flags PDFs as modified?

My son is having problems submitting financial documents to a leasing agency because the third-party certifier reports that his downloaded statements appear modified. That isn't the case.

I examined some of the PDFs with the "mdls" command in Terminal.app and noticed that unlike documents downloaded on the Windows platform, there is a line in a Mac document (both Safari and Chrome) that says:

% mdls <name of PDF>
...
kMDItemEncodingApplications          = (

    "3-Heights\U2122 PDF Merge Split API 6.27.2.1 (http://http://www.pdf-tools.com)"
)
...

However, if I display the PDF in the browser and print-to-PDF to save the document instead, the tag is this:

kMDItemEncodingApplications        = (

    "macOS Version 15.2 (Build 24C101) Quartz PDFContext"

)

Windows PDFs have no such tag.

Has anyone else noticed this? Can it really be the case that the creation tags on Mac PDFs are enough to flag PDFs as modified, and that every Mac user is susceptible to the same problem?

MacBook Air, macOS 15.2

Posted on Jan 2, 2025 12:21 PM

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Answer 1

etresoft

Level 9

56,668 points

Jan 2, 2025 2:34 PM in response to Jeff Bailey

Jeff Bailey wrote:

It’s that rightmost button I’ve already been using to download the documents, documents that point to www.pdf-tools

Earlier, you specifically said, "print-to-PDF to save the document". That will generate a new PDF using Apple's software as described in your initial post. Just clicking the download button does not do that. But if you print to PDF, then it will be re-generated. In some cases, even opening a document in Preview will modify it. I just did a test and merely opening the document didn't change it, but you could see different behaviour with different files.

I’m wondering what’s flagging the document as modified by the AI that’s reviewing them

It's definitely not any kind of AI. It's not doing anything differently than what you are doing. It's probably looking specifically for the string "Quartz PDFContext" and a few other popular consumer tools. A downloaded document that they would accept would never be created using such tools.

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Answer 2

etresoft

Level 9

56,668 points

Jan 2, 2025 5:21 PM in response to Jeff Bailey

Jeff Bailey wrote:

METHOD 1: none

Maybe copy that files to the Mac and run mdls on it there.

The only thing I know for sure is that the algorithm flags the METHOD 2 document as being modified and rejects it. We will be submitting the METHOD 1 document instead to see if that is accepted as genuine. If it is, I want to know how that tag gets generated and why a MacOS-only feature is grounds for rejecting the document when its Windows counterpart is not.

Downloading is downloading. There isn't any difference between Windows or Mac. It is possible that this PDF is being generated dynamically and it's giving the Mac a different file than it gives Windows. You should be able to test that easily enough. You don't even need mdls. Just compare the checksum of both files.

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Answer 3

varjak paw

Level 10

182,668 points

Jan 2, 2025 1:37 PM in response to Jeff Bailey

I'm not seeing that flag PDF Tools in any document I have, even one I've just modified and saved, with Preview. Are you or your son indeed using the Preview app, or is another app being used? If it's a third-party app, they're probably using the code from PDF Tools to create their app. He might want to try Preview or Acrobat Reader, if these are fillable forms.

As to what is causing the document to be rejected, that would be something you'd have to ask of the leasing agency.

Regards.

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Answer 4

Jeff Bailey Author

Level 2

291 points

Jan 2, 2025 4:33 PM in response to etresoft

etresoft wrote:

...

It's definitely not any kind of AI. It's not doing anything differently than what you are doing. It's probably looking specifically for the string "Quartz PDFContext" and a few other popular consumer tools. A downloaded document that they would accept would never be created using such tools.

I agree, it's not AI in the usual sense, but that's what the lending agency has reported as triggering the error at the third party who checks the documents. But we can't engage with the third party directly, so I'm wondering what the heck they could be seeing.

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Answer 5

etresoft

Level 9

56,668 points

Jan 2, 2025 12:55 PM in response to Jeff Bailey

Jeff Bailey wrote:

My son is having problems submitting financial documents to a leasing agency because the third-party certifier reports that his downloaded statements appear modified.

That's a clever new trick.

However, if I display the PDF in the browser and print-to-PDF to save the document

That's the problem. If you print-to-PDF, you are creating a new PDF document.

What you want to do instead is move your mouse cursor down to the bottom of the screen, towards the middle. These hidden user interface controls will appear:

Click the rightmost, download button to download the PDF.

Has anyone else noticed this? Can it really be the case that the creation tags on Mac PDFs are enough to flag PDFs as modified, and that every Mac user is susceptible to the same problem?

Only honest people would notice this. It would be easy to modify the the documents in any way, to say anything you want, and they wouldn't be able to tell the difference.

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Answer 6

Jeff Bailey Author

Level 2

291 points

Jan 2, 2025 1:25 PM in response to etresoft

“Only honest people would notice this. It would be easy to modify the the documents in any way, to say anything you want, and they wouldn't be able to tell the difference.”

Of course, but I’m wondering what’s flagging the document as modified by the AI that’s reviewing them.

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Answer 7

Jeff Bailey Author

Level 2

291 points

Jan 2, 2025 1:29 PM in response to etresoft

It’s that rightmost button I’ve already been using to download the documents, documents that point to www.pdf-tools

Only happens on the Mac AFAIK.

[Edited by Moderator]

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Answer 8

Jeff Bailey Author

Level 2

291 points

Jan 2, 2025 4:51 PM in response to varjak paw

varjak paw wrote:

I'm not seeing that flag PDF Tools in any document I have, even one I've just modified and saved, with Preview. Are you or your son indeed using the Preview app, or is another app being used? If it's a third-party app, they're probably using the code from PDF Tools to create their app. He might want to try Preview or Acrobat Reader, if these are fillable forms.

...

Wow, this is very confusing. I'm reporting what I see via mdls without ever opening the PDFs in Preview.

Windows:

Visit financial agency site in browser (Chrome). Click icon to display statement of interest. The PDF is opened in a new tab.
Click icon to download the document to computer.
Document saved to iCloud. Never opened in Acrobat or anything else. METHOD 1

MacOS:

Visit financial agency in browser (Chrome or Safari), PDF opened in new tab.
Download document
1. either by click the icon to download it (METHOD 2), or
2. Print-to-PDF via print dialog (METHOD 3)
Document is never opened in Preview or Acrobat

Metadata visible in MacOS via mdls command:

METHOD 1: none

METHOD 2: kMDItemEncodingApplications = ("3-Heights\U2122 PDF Merge Split API 6.27.2.1 (http://www.pdf-tools.com)")

METHOD 3: kMDItemEncodingApplications = ("macOS Version 15.2 (Build 24C101) Quartz PDFContext")

The only thing I know for sure is that the algorithm flags the METHOD 2 document as being modified and rejects it. We will be submitting the METHOD 1 document instead to see if that is accepted as genuine. If it is, I want to know how that tag gets generated and why a MacOS-only feature is grounds for rejecting the document when its Windows counterpart is not.

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