find out changes

[daniela_sch]

how to find out the changes made to the PDF file before receiving it

[try67]

Changes compared to what? You can't find out anything until you've received the file and can compare it to something else, like a previous (or different) version.

[daniela_sch]

Thanks. My problem is : i recive from an office a PDF file. I have to find out if this file (which I have never seen and of which I have no other versions) has been manipulated and if YES, how. Could you help me? many thanks

Daniela

[try67]

Unless you have something to compare it to, I don't see how that is possible.

[daniela_sch]

Thanks. There is no way to discover if if a part of a PDF document has been changed? A register of changes made for example, to see the author, the date or something similar. In my case i need to evaluate in contable document if any sum or value has been changed

Thanks

DS

[try67]

There might be a register of previous versions, called PieceInformation, but it won't contain any info on who did them, and it's not simple to access it.

[daniela_sch]

Thanks. But it shows what is the modify part of the document ?? It would be a start for me....

[MikelKlink]

There is no way to discover if if a part of a PDF document has been changed? A register of changes made for example, to see the author, the date or something similar.

Well, there is no requirement for a PDF processor to add a hint that they have manipulated a document. There are certain PDF parts where programs can add such hints (Info dictionary, metadata stream, ...). But on one hand you say you don't know what the original document looked like, so maybe such a hint you find may already have been part of the original. And on the other hand someone seriously trying to manipulate the PDF will choose a PDF processor that does not leave such hints unless they are dilettantes.

You'd need either the original or at least a secured fingerprint thereof, e.g. in the form of a digital signature by an identity that for sure is not involved in forgery.

[daniela_sch]

Thanls, i know...... but i'm in a difficult situation

i don't know how can i reach the result

i have many contable documents and i need to know if they are true.... and i can't log in the original information because they are privat informations.....

many thanks to all !!!

[try67]

The bottom line is this: Any changes to a PDF can be made "invisible", unless that file was previously digitally signed.

[daniela_sch]

I find the solution !!!!!! I did the tests with a file modified by me. I transform the modified file into html then I read the code: where it has been modified it returns a string (now I'll see how to translate it) where it has not been modified it returns the plain text value of the document. So I can find WHAT was changed even if I can't know the previous value. but I can get to the previous value with the inverse formulas. At the moment is the best first dolution

[MikelKlink]

Please be aware that that won't identify changes applied by a decent forger.