Navigate to the message with the attachment and there should be an option in the email to save the attachment.

 

I couldn't figure this out either. I sent myself a small pdf file and then opened the email on my phone with the Gmail app. The only option there was "View". No download or Save option.

I then ziped it and sent it to myself again. Once again, the same option for a zip file... View and no Download or Save. Longpressing on the file does nothing and there doesn't appear to be any other options for saving these file types in the Menu.

 

Install the free Adobe Reader app.

A download button will appear so you can store the pdf on the sd card. It puts it in the Download folder on the sd card. The app can be moved to the sd card to free up memory (don't have to be rooted). It also has an option to share via bluetooth so I suppose you could print it that way if you have a bluetooth capable printer.

 

I tried that app... no download button in the email for me. Just the same preview button. Even when it's opened in the reader I cant locate a save button.

 

Try Download All Files, it asks where you want to save the file.
https://market.android.com/details?id=com.hwkrbbt.downloadall