Ok, so I have sent a copy of this to my home and opened it on my PC and laptop and no problems so guessing this is going to be fine now and that for whatever reason the couple of PC's I have looked at it on at work have some sort of setting that is different that causes the corruption.
The idea of the application is that pages 1-3 are completed and emailed back and paeg 4 is to be printed, filled in and faxed or sent back by post. So it wouldnt work if PDF and we already have one on our website, the idea was to change to this format to make it easier for the students and for us to administrate. So for now I am going to close this as complete, unless I get an influx of people telling me otherwise when I put it on the website!
Ive also made the font changes as suggested, not sure why they would have changed whilst I was making this form but hey-ho.
Thanks again for all your input and I'm sure I'll be back with another problem soon! (although hopefully I can also offer someone some help in the meantime)