How would you distinguish if the file actually contains a + followed by a valid character code (e.g. that the user typed&saved and is now part of the file)?
In fact, only the InkNameL part of the line is encoded like that, rather than the whole file. The equals characters should be +AD0- according to the lookup table URL I posted.
See the Wikipedia article on UTF-7, which is what your files seem to be. That gives an algorithm for decoding. Also it doesn’t look like this format has anything to do with the Mac, which isn’t mentioned in the article.
Right. If the user can’t save himself/herself to the file and you always know where to expect encoded or clear strings, you’re good to go. I thought you didn’t know the saved pattern too.