My company is putting me up in a corporate rental for months and I didn't bring a printer from home. I needed to sign some legal documents just now, but couldn't print them from an email attachment.
So I just googled "how to sign documents on iPad" and found a blog post that someone wrote, with instructions and an app recommendation. I didn't bother reading the directions on the blog or the app. I just bought it, bumbled my way around and was able to create a copy of the PDF form, sign it with my finger and email it.
I CC'd myself to see what the recipient would receive. Worked perfectly!