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Can someone help me understand why the following command will overwrite the Title tag, but not delete the subject tag of my PDF file?
exiftool -Title="My Title" -Subject= myfile.pdf
Thanks!
R.
mrgou
Posted 2020-01-22T19:48:31.270
Reputation: 137
Removing PDF Subject Tag with Exiftool
Answers
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The detailed answer was discussed here.
mrgou
Posted 2020-01-22T19:48:31.270
Reputation: 137
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Exiftool uses an incremental update method, part of the 1.7 PDF specification. This type of update is reversable, as mentioned on the ExifTool PDF tags page. In order to remove the old data, you would have to re-linearized the file with a program such as qpdf.
The example file your provided on the ExifTool forums created with PDF Creator showed that the value you used for Subject also was added to the XMP:Description tag. As these two tags are corresponding, Adobe Reader will display data from either tag as the "Subject".
StarGeek
Posted 2020-01-22T19:48:31.270
Reputation: 782
Linearization with qpdf does not appear to work. Acrobat Reader DC still displays the original value in the Subject field... – mrgou – 2020-01-24T17:42:35.800
What version would it be? "exiftool -ver" – Gerard H. Pille – 2020-01-22T20:07:15.417
I have version 11.84 – mrgou – 2020-01-22T20:15:51.040
Do you end up with an empty Subject? – Gerard H. Pille – 2020-01-22T20:20:01.770
What program are you using to see the "Subject"? Does the
– StarGeek – 2020-01-22T21:02:54.350Subjectstill appear if you run the command in exiftool FAQ #3 or does the value appear some place else?The value still shows in Acrobat Reader DC, as well as PDF Architect, but indeed not with
exiftool -a myfile.pdf(the tag is not even listed). A bug in exiftool? @GerardH.Pille: no the value of Subject is left unchanged. – mrgou – 2020-01-22T21:40:48.4531Then I would deduce that the tag is not really "Subject". Would you mind showing the output of "exiftool myfile.pdf" ? – Gerard H. Pille – 2020-01-23T15:50:20.807
@GerardH.Pille Your hunch was correct. An additional tag had the same data and Adobe Reader was pulling from that. – StarGeek – 2020-01-25T16:59:24.490