How do I upload files onto Pages on my iPad?

You can email them to yourself and then open them in Pages by using the "open in" option in the mail app when you are viewing the attachment, you can use DropBox, or you can use iOS file sharing.

Connect the iPad to your computer and launch iTunes. Click on your iPad's name on the left side of iTunes under "Devices" in order to select it. Click on the Apps Tab in the iTunes window on the right. Find the Pages App in the list of File Sharing apps under the main list of apps and click on it. Then drag the files from your desktop that you want to move into the document sharing window on the right - next to the the Pages app. You can also use the Add button and navigate to the documents that way to select them. Sync your iPad if you choose to do so and then eject it when the sync completes.

Launch the Pages app and then click on the + in the upper left corner to add a document. Select - Copy from iTunes and a window will pop up with a list of all of the documents that you dragged into the window on the computer when the iPad was connected to iTunes. Select the document from there.

This article explains if for you as well.

http://support.apple.com/kb/HT4088

iWork: Pages, Numbersm Keynotes; also tie into iWorks.com. So if you have iworks on your computer. You can upload files ot iworks, and then download the files on the iOS device.

There are also products like i-FlashDrive. (a usb flash drive, that also has a dock connector to connect to the iOS device.)

Many iOS applications support webDav. There are lots of companies that offer webDav hosting.