Mail merge works, but it may be overkill for the needs.
The easiest way is have the original text entered into formfields. Say you have five formfields (FirstName, LastName, Address, City, AccountNumber)...whatever, I am making this up. It is important to name the formfields. Do not accept the default names of Text1, Text2 etc.
Make sure the formfields are set to Calculate on exit. Right click the formfield, select Properties - check Calculate on exit. This is also where you name the formfield.
So, on the first page, have the formfields, something like:
LastName
FirstName
etc
etc.
Formfields MUST be inprotected sections. After the formfields themselves, if you want user to be able to edit things, insert a section break (Insert > Break). Then protect the section with the forms (Tools > Protect document > Forms) - you can choose what sections to protect.
I know this sounds complicated, but it isn't really.
OK, now, here is the real easy part. ANYWHERE in the document, and AS MANY times as you want, you can insert a field that will always hold the information from a named field.
For example, to have the same information as the FirstName formfield:
1. Go to where you want the duplicated information.
2. Press Ctrl-F9. It inserts curly brackets. Do NOT type in the curly brackets. You MUST use Ctrl-F9.
3. Type in the name of the formfield you want the info from.
That's it. You are done. This field will update to the named field. It will look like { FirstName }.
Gerry