This posting answers a closed thread with similar title posted 5 Oct
2003. I'm posting this as I've found the answer.
Basically, the thread referred to problems with placing a plain text
file in PM7.0. It gives an error - cannot find filter for requested
operation.
I've found that the reason it gives this error is that the filter is
not there! Also, you can't find it on the Adobe site. And it's not on
the PM7.0 installtion disk!
However, if you copy the relevant filter from a copy of PM6.5, then all
works as it should.
The filename is TEXTIMP.FLT and you'll find it in the
\RSRC\UKENGLISH\FILTERS folder. Copy it over to the same folder in the
PM7.0 installation.
I hope this is of help to others with this problem.