Comment 62 for bug 1389723

I agree with Jabier.
The conversion must be applied only once, to "old" documents and before any other operation is performed; hence the information is needed only in that moment and no more. As the document already exists, you can't count on new fields being present (I'm thinking about all the documents I've generated so far and now archived: what if I need to modify one of them to make a new release?).
The viewbox should also be fixed if it needs to be made compliant to 0.92.
IMHO it's important that at least 0.91 is not going to generate documents difficult to convert.