You can freely and lawfully download a printable score for this Work from IMSLP - the Petrucci Music Library - though it may not be exactly the same as the one used to make the Midi Files below, and it probably won't be as good as a proper paid-for engraved and printed score.
There is an excellent performance of the Work on YouTube starting here.
The Files below were prepared from a very old Schirmer Score, and although ostensibly the Work requires three Choirs, in fact, because the vocal forces are shown as divided STB, ATB and SA, it is evident from the Score that really it uses only 1st and 2nd Choirs, with the "3rd" Choir voices being in effect merely the Sops of Choir 2 and the Altos of Choir 1 (neither of which are ever used for themselves, and which only ever sing together).
Here is a "clickable" Table of the available Midi Files for this Work (note that in some of the sections one or more Voice may in the score be divided into two for a few bars/measures, but that they are not so divided in these Files):-
| Bass 1
|1: Te Deum
|2: Tibi Omnes
|3: Dignare, Domine
|4: Christe, Rex Gloriae
|5: Te Ergo Quaesumus
|6: Judex Crederis
|7: March (for the presentation of the standards)