Data Security Issue - Printing PDF - "deleted" information gets printed

Question

The Problem

I recieved a pdf file at work which I then printed. In the pdf file there were several optional fields where one could enter information such as "place of birth" etc. If I open the pdf file on my computer, I can see a set of input information A (a travel request with dates from this year 2017).

If I print the pdf on the local printer, the printed document contains a set of information B which for example contained travel request dates from 2015. This information was not visible when opening the file on my computer. I have been able to reproduce the error multiple times.

Why is this a problem?

It seems that previous entries into the pdf were yet somehow stored in the pdf contrary to what was visible when opening the pdf. When printing, the printer seems to access only the oldest entries and prints those.

This is a potential breach regarding data privacy and security since the pdf file seems to save all previous entries without anyone knowing.

Especially at work, some of these pdfs contains bank account information and other identity related information.

The Question

Did anyone experience a simliar issue or knows how to delete the invisible old information yet stored in the pdf?

UPDATE1: I could not reproduce the error on other printers. It seems this error is caused by the specific printer. Yet the information must be present in the PDF file, which is the specific cause of my question.

UPDATE2: Using the information from the accepted answer, I used the program "PDF CHAIN" and selected the option "drop XFA from document". I then saved the manipulated document again and printed it on the same printer. Finally, the correct information was printed.

Answer 1

At a guess (and that's all it is without being able to see the original file) the PDF contains optional content or annotations which contain different field data for Print and Screen.

If you open the file using a PDF consumer (eg Acrobat) then what you see is the 'screen' result. Depending on the consumer you are using it may then either send the screen data to the printer, or substitute with the 'Print' data.

The printer you note as being a problem is capable of direct PDF printing, you haven't stated if that's how you are printing the PDF file, or whether you are using an application, nor whether the other printers are PDF capable or not.

My guess is that there is a different decision being made somewhere in the 2 print paths as to which is the 'correct' information to print.

Note that this does not mean that the PDF 'seems to save all previous entries without anyone knowing'; that's not really possible with a PDF file.

A malicious PDF processing application could do so, by adding comments to the PDF file, but only that application would be able to retrieve it.

But it is possible to have multiple entries of different types for different purposes, and if they aren't the same (because of the tool used to edit the file) then you can get strange results like this.

Note that if this is a problem for you then you probably shouldn't be using PDF, but you can mitigate the issue by digitally signing your documents. Signed PDF files include means (secure cryptographic hash) for verifying that the document has not been tampered with . Of course, you can't then edit the PDF file without re-signing it.

Oh, one other possibility would be that the PDF was actually an XFA form; its possible to have part of the document be a valid PDF which prints 'something' when a PDF consumer can't handle an XFA form, but that need bear no relation to what you see when you use an XFA processor.

My money's on optional content, AcroForm fields, or annotations where the Print data is different from the Screen data though.