Taking out the metadata won't help you as there are no guaranties that the
layout engine is the same from version to version, the text may look the
same but the internal representation is different. The best way is to do a
checksum to the text (words only, skipping the whitespace) and store that
information in the pdf metadata as a new key. The already generated pdf can
have the text extracted, the checksum calculated and applied to the same
pdf.

Best Regards,
Paulo Soares

> -----Original Message-----
> From: Matt Benson [SMTP:[EMAIL PROTECTED]]
> Sent: Tuesday, November 26, 2002 15:40
> To:   itext-questions
> Subject:      [iText-questions] PDF metadata
> 
> We are using iText to convert text files to PDF as
> outlined in the FAQ.  This works; however I want to
> take a checksum of the PDF created and use it in
> conjunction with some other information to verify we
> have not created this file before.  What I am finding,
> however, is that the metadata of the PDF always
> differs between iText versions as well as creation
> date/time, so I cannot create the exact same file
> twice and thus cannot rely on a checksum.  I could use
> the checksum from the input file, except that this is
> a modification to a production application and we no
> longer have the input files for the existing data.  So
> to do this I would have to extract the text to get an
> approximation of the original file.  If I did this,
> the checksum would represent slightly different things
> from the old to the new data.  What I am wondering
> about is whether these variable pieces of metadata are
> vital to the PDF structure, and if not, what would it
> take to remove them?  Alternatively, if anyone has a
> better idea then those are welcome too.
> 
> Thanks,
> Matt
> 
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