there are various tools online to view PDFs without even downloading them. For example, google docs has one: https://docs.google.com/viewerng/viewer?url=https://software...

Are you using a rooted Android phone? There are open PDF readers that you can flash as an apk into your rom image, if you’re trying to avoid spammy adware from the market. Apple supports PDF files on iPhones natively, by default.