needing to add extra addresses in sending documents

Printed, PDF or Email?

Assuming Printed or PDF for this response...

1. You could display the addresses in a 6 row portal set to slide up. You have limitations with this approach and if you ever get more than 6 addresses, the 7th address won't show.
2. If your addresses are stored in a related table as they should be, base a layout on this table of addresses. Put the addresses in the body and put the document text in a Trailing Grand Summary part. You might want a Join table to link addresses to your document text. If so, make your join table the referenced table in layout setup and add the document and address fields from related tables.

Use sliding/printing to remove unwanted spaces.  This feature shrinks your field to fit the data.

In layout mode, right click on your address field and choose Set Sliding/Printing.

Check "Sliding up based on" and choose how you want the field to slide.  You probably also want to check "Also reduce the size of the enclosing part" this will slide up the whole layout part (aka body, subsummary) along with your field.

You won't see any difference in Browse mode but the sliding will take affect when you enter preview mode and when you export your letter.