Any UMPC will let you do what you need, so get the best deal you can get.
Remember a UMPC is a full computer, so you can do with it everything you can do with any portable, so you will be able to use it to create text files, browse web, etc… etc… etc…
I myself have an Asus R2H with windows xp tabletpc and it serves me pretty well (come with 512 Mbyte of ram upgraded it to 2 Gigs).
When I bought it, it was full of crapwhare - “free and other” software Asus have put in it and who just did put into a crawl, so I have had to uninstall all the unnecessary crap (information online exists on how to do this). Once done, it runs as good as any one of my (or our company’s) tabletpcs, even if it’s just a celeron 900.
BTW: I advise you to stick to the 7” UMPC’s.
Also it’s a great eBook reader and lets you access all the pdf files you want without a problem.