Adobe Acrobat + Latex Fonts

I opened a .pdf file in Acrobat 7.0 Pro and I try to make some text
modifications but I get the following message :
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"All of part of the selection has no available system font. You cannot
add or delete text using the currently selected fonts"
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which is right as this document (Latex origin) uses some embedded
subsets from CMR - Computer Modern Roman) CMBX, CMSY... and some
embeddded subsets of True Type fonts...
can I substitute my fonts to these ones ? if yes I should I proceed to
be able to modify this pdf file ;
the original file doesn't exist anymore and I don't want to loose
formatting (no .doc conversion..) as I have minors changes to write ?

thanks

Joss