In a slightly roundabout way, iAnnotate can create PDF documents out of Word, Excel and Powerpoint documents. It's a new experimental feature of iAnnotate (one you have to turn on within the app).
The easiest way is to have a document either in Dropbox or e-mailed to you. Select the "Open In..." feature to open the document in iAnnotate (note that you must have already turned on the experimental feature first - in iAnnotate's settings).
When iAnnotate opens, it'll automatically open the file as a vector PDF - you can write, highlight, add notes, etc. on it. Then, when you are done, you can e-mail it as a PDF, either back to yourself or to Dropbox as an attachment (iAnnotate is working on the ability to send the altered file back up to Dropbox). Oh, and you can e-mail the original file as a PDF with no markups, an editable PDF or one that's flattened (changes are "baked in"). Regardless, you would then have a PDF document.
It sounds a bit complicated at first, but it is much easier than it sounds (or how I describe it). In addition, iAnnotate does have an internal web browser, so you can download files that way, also.
I like this feature of iAnnotate and think it's a great way to mark up .doc(x), .xlx(s) and .ppt(x) files - along with PDFs! Also, it's a great way to create PDFs out of these types of files. Of course, and as always, YMMV.
Marilyn