Please keep in mind that most, if not all, tortoises do poorly in pairs. Much like beardies, they aren't exactly social animals and do best kept singly. Redfoots are the possible exception, with some showing social behaviors, but even then there are those who don't play well with others and the situation should be watched closely.
Anyway, the problem with pairs is that the dominant tortoise will focus its entire bullying/domination efforts on the single less submissively tortoise. This isn't such a problem with a group, where that negative attention is spread out between 2+ other tortoises, so the submissive torts all at least get a reprieve when the dominant tort's attention is on a different tortoise, but with a pair, that negative attention is directed at the lone submissive tortoise 24/7. That much wear and stress creates a multitiude of problems, ranging from weakened immune system to lethargy to not being able to eat at all due to the dominant tortoise not allowing it. Some people manage to get by with tortoises in pairs, but more often than not, it ends with one tortoise becoming very ill.
For Hermann's tortoises, the bare minimum for one tortoise is 4x2 feet of space. Again, that's absolute minimum. Ideal for any tortoise is as big of an enclosure as you can fit, but for the Hermann's, at least 6x2 feet floorspace.
For the Redfoot, which are usually quite a bit larger, you miht be able to get away with 6x2 or 6x3 feet minimum, with ideal being 8x4 ft or larger.
With either of these, it's best if you can provide a large, secure outdoor enclosure for when the weather is nice.
Now, if you're housing a pair or a group, there are a couple things to consider. Obviously, you need to increase the space of the enclosure. The very largest you can provide is best. There needs to be enough space for many different hiding places and line of sight blocks, such as plants, so they aren't constantly having to look at each other (again, torts are generally solitary). Second, they benefit immensely from multiple everything. Multiple basking spots, a couple different feeding stations, even 2 water dishes, so they don't have to share, and so there's always a back up if one tortoise decides one particular basking spot (or food pile, etc) is his and his alone.
I nearly forgot. If you do decide to try a pair, make sure you have a pair of females. Mature males are especially territorial and may go so far as fighting to the death, and, with a male/female pair, the bullying stress is increased that much more by the male trying to fulfill his breeding instincts.
I hope that helps some. You can find great care info on many different tort species over at TortoiseForum.org.