From an IT pro: #1 most essential – GoodReader PDF Editor & Viewer Review

I'm an IT professional and I bought this on sale after Slickdeals folks ranted and raved about it. Since then it has identified itself as by far the #1 most useful purchase on my phone and tablet by far. The number of uses are countless--it's much more than a PDF reader. It can download many files my phone can't, unzip stuff, and is great for even just getting particular files opened in the app you want.
Review by Crimson Tragedy on GoodReader PDF Editor & Viewer.