Use your iBooks library:

1. In your iPad or iPhone, open the email containing the download link that you received after you finished placing your order. (Other tablets and cell phones have similar book reader apps.)
2. Click the download link to open the PDF or doc file.
3. Once it's open, click on the “Open in iBooks” button in the upper right corner. This stores a copy in your iBooks library for accessing later. Now you can access that PDF from iBooks, anytime.

Or use the GoodReader app:

1. Download it first in your laptop or desktop computer and save a copy there.
2. Download the GoodReader app from iTunes.
3. Transfer it from your computer to iTunes.
4. Open the document in GoodReader.