I have many years of dealing with the military travel issue (and some of the interactions were quite frustrating).
USUHS students have problems with this sort of thing. HPSP students have HUGE problems with travel vouchers. (Please note, I'm not pointing the finger at the student, I'm pointing it at the system).
What finance office do you have to file with? (Varies by Service).
Do they accept travel vouchers and supporting documents by e-mail?
The e mail with scanned receipts, orders, etc, as .pdf attachments works great (especially the return receipt requested option) *if* the finance office you have to file with will accept them. Some will, some won't. I've filed 20 page vouchers this way.
If they won't take e mail, will they take fax (at least you have the original forms and receipts and a transmission verification)....
Concur with writing "Supplemental" if you want more money on a partially paid voucher or "Resubmission" if you didn't get paid at all.
Also, concur with keeping copies. Keep them (hard or e copy) for at least 3 years including the settlement voucher. I know someone who was told to repay a travel payment because the voucher got "lost" and the assumption was it was an erroneous or fraudulent payment. Fortunately, he was able to present a notarized copy of the settled voucher to end the issue (he kept the original, of course)....