Creative Suite from Adobe for starters, if you're not doing any design you could probably get by with just Acrobat Professional. Most customers at a small shop like to bring in stuff like Microsoft Office and they'll have the latest version so you'll need that. I also recommend some sort of imposition software, either Quite Imposing or Debenu Aerialist work fine for SRA3 digital stuff. You'll also want a copy of Enfocus Pitstop Professional. I would consider these essential to running a working shop. If you start doing design or touching up other's design you'll want to get Creative Suite from Adobe with Indesign, Illustrator, and Photoshop (if you can I would recommend buying CS6 rather than moving to the Creative Cloud versions...personal preference). Other nice software to have are things like an estimating package, accounting software like Quickbooks, OCR software like Omnipage Professional, mailing software like Satori Bulk Mailer or Melissa Data, VDP software such as Fusion Pro, XM Pie, Pageflex and the like. I've also found little pieces like PDF protection removal, timeclock software, and DVD/CD burning software are very handy.