You will need to create a text file containing the filenames for all the pages that you want to add. Create a new Publisher document with just one page, and add a Picture Frame to cover the full page. Fire up the Data Merge Manager, and specify the text file containing the filenames as the source for the data merge. Select the image frame, open the Fields panel and double-click the field containing the filename. Then generate to create a new Publisher file containing all the pages. Finally export as PDF to create a single PDF containing all the pages.