Fairly sure that this is a really dumb question and the answer is no but I thought I'd ask just on the off chance someone knows a clever way of doing this.
 
I've just got a midi file back off a keyboard player to drop into a track that has a 6/8 time signature.  However the guy has recorded it in 4/4 so it obviously doesn't fit my grid which is a shame because its great playing.  Is there a clever way of using the midi pattern tool and paint in Platinum to paste it into my grid so it fits the 6/8 timing whilst retaining whats he's played?

I think I just thought of a way unless any else has a better idea....
 
If I import the 4/4 midi file into a new half time 4/4 session (eg 55BPm as opposed to 110 BPm 6/8 session) then I export it as a wav.....I could import the wav into the 6/8 session and use melodyne to convert it back to midi should I want to change the part in some way

How about the Step Sequencer.
Drop the file into a midi track; Launch Step Sequencer, as it defaults to 4/4
Then change the Step Seq. values to 6/8
It should move the notes to suit.........
 
p.s. I have never done this, but it argues in my mind it may work

6/8~3/4...is to what?...6/8~4/4 means a 1/4 note or 2x1/8 rest might be needed added in all of the 6/8 reducing process to sync to 4/4?

I can't personally grasp how it could be done within the standard program. Not to say that it can't, but I just don't have the know-how.

That said, this is at least a minor chance to mention an awesome tool called Stylus RMX. This tool does that kind of stuff without even blinking. I happen to have it, so if I was doing that I'd use Stylus RMX.

Now, back to regular commentary.

does  6/8 reduces to 3/4 eh?...if 1/4 note is missing you can cut that up and add into the bar the "missing value" in terms of= rests/cut space ,/or add in note of 1/4 note divisions to align to 4/4....not sure but it sounds sort of something a liken to?

This may be a chance to see if the midi stretching ability works for this. sort of thing

Sir Les
does  6/8 reduces to 3/4 eh?...

Yes. At least for our purposes.
The metronome is your friend here. We can take advantage of the complimentary 2/4 riding with the 6/8.
So setting the meter to 3/4 and doubling the BPM gives us a nice 6/8.
The 2/4 also gives us another edge. Both 4/4 and 6/8 will sync to it.
P-Theory, if you can find that sync, you may be able to fit his 4/4 stuff into your 6/8 project. It could be interesting.
My latest project involved this very overlay.