Another solution which may be worth looking at is to convert your pdf to postscript (with something like ghostscript). Postscript is an open format and the file format is text so you can edit it any-way you like with perl :) It wouldn't make a lot of sense to go this way if your template was changing often or if you were doing a substantial edit but for changing one value (if I have understood you correctly) it might be a neat hack.

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Until you've lost your reputation, you never realize what a burden it was or what freedom really is. -Margaret Mitchell