Clicking Join | Join Pages will combine selected pages from many different documents. This operation will move all selected pages in the Separation Workspace to the right of the first page selected. Pages will be joined in the order in which the pages were selected.
This option is not available in Document Display Mode.
If a page is selected from a locked document and a Join Pages operation is performed, the page from the locked document will be copied and joined to the right of the page from the unlocked document. If the locked page is selected first, the pages from the unlocked documents will be added to the right of a copy of the locked page.