After the Documents Packages window has been opened, additional documents can be added to the package using the Add Documents button.
To add additional documents to a Document Package:
The newly added contents are displayed at the end of the Included Documents list. When documents are brought into the package in this manner, they are added to the Other Documents document set.
After additional documents have been brought into the package, they can be selected or deselected as needed according to the steps found in Selecting Included Documents, or can have their pages adjusted using the steps found in Selecting Included Pages.