To install paid apps, Go to Appstore>Purchased tab>Tap the cloud icon on the app you want to download.
To transfer documents, u'll need a app called 'Pages', Go to icloud.com>log in with your apple ID>opens iWork and drag the document u want to the space in pages tab. Make sure you enable your iCloud in 'Pages' app, your documents will automatically download to it.
iOS: Troubleshooting Siri
Your tags show iPad. You need the iPad 3 or newer in order to have Siri. What iPad do you have?
There are a number of apps that are compatible with Word....Documents to Go, Pages, Quick Office Pro .... You need an app that will read, save and Word files on the iPad and if you don't have such an app, all that you can do is email the file and read it in the email. You will not be able to save or edit the files.
After you download one of this apps, you can use email, DropBox, and IOS file sharing in order to transfer the documents back and forth. You can use iCloud as described above with Pages or any other app that works with iCloud.
Read this to learn more about file sharing.