I can't download PDF files or excel files from my email

You are saying that files are not opened in the mail app when you are reading the email or the file does not open when you tap on the icon?

Try quitting the mail app and the launch it again. Try restarting the iPad as well.

To quit the mail app .... Go to the home screen first by tapping the home button. Double tap the home button and the task bar will appear with all of your recent/open apps displayed at the bottom. Tap and hold down on any app icon until it begins to wiggle. Tap the minus ➖ sign in the upper left corner of the app that you want to close. Tap the home button.

Restart the iPad by holding down on the sleep button until the red slider appears and then slide to shut off. To power up hold the sleep button until the Apple logo appears and let go of the button.

Have you tried emailing a PDF file to yourself? The reason I am asking is so that you can test to see of the files have been saved properly.

When you say download - you do just mean open the files correct? You can't save the files unless you have a compatible app on the iPad.

I really don't know what else to suggest but try this bizarre workaround. Forward any of those emails to yourself and see if you can download or open the attachment from the forwarded email.

I can't open too. I try my iphone4s and ipad2 both can't open.

I have reset my ipad2 but it still can't open file in my Email.