Q. I'm looking for an English translation of Diocletian's Edict on Maximum Prices.

1) The most quoted/cited source for the English translation is in the book "An Economic Survey of Ancient Rome, Volume V: Rome and Italy of the Empire" that was edited and compiled by Tenney Frank in 1940. You can submit an interlibrary loan request for the fifth volume in this series. The translation itself was by Elsa Rose Graser. This translation is incomplete. A couple of new fragments were appended by Graser herself in...

2) Transaction of the American Philological Society, 1940, volume 71.  The title of that is "The Significance of Two New Fragments of the Edict of Diocletian" and you can find it by doing a search in our collection in the JSTOR database.

3) Dr. Jacqueline Long, from the Loyola University Chicago, has translated the preamble:  http://orion.it.luc.edu/~jlong1/priceed.htm

4) "Important new fragments from the copy found at Aezanis are edited and published by M. Crawford et al., ZPE 26 (1977), 125-51 and 34 (1979). 163-210." at http://www.tulane.edu/~august/handouts/601ccdoc.htm . I believe that ZPE refers to Zeitschrift für Papyrologie und Epigraphik. 

You will find some extractions from the Edict on Maximum Prices at the following Websites, but I would not feel comfortable citing any of these sources in a college-level research paper.

What things cost in Ancient Rome
A list of prices and wages extracted from Diocletian's Edict on Maximum Prices (301AD). The extracts were selected by Mike Dalka, Ancient Coins for Education, who also wrote an explanatory commentary.

The Edict on Maximum Prices
Another list of prices and wages extracted from Diocletian's edict.