If you use Preps to gang Prinergy pages, page aliases—instead of copies—are created in the ganged job to help you manage changes.
Page aliases are links that are created from the original page to the ganged job. Page aliases provide many benefits over copies, and are automatically created when the populated imposition is imported into Prinergy from Preps.

Benefits of page aliases

Page aliases provide the following benefits:

• Page aliases save file space because pages are not duplicated.
• Page edits are easily managed—for example:
  • If a page's contents are updated, when output, the alias automatically picks up the latest updates of the original. There's no need to duplicate the updated content to the alias.
    Note: This benefit applies to simple updates only—for example, text changes. Some changes, such as changes to the number of inks or geometry changes, may invalidate the existing ganged imposition. In this case, you will likely need to rebuild the ganged imposition.
  • If the approval status of a page changes, it is reflected in both locations.
  • If the page geometry of a page changes, it is reflected in both locations.
• History entries about ganged pages are logged in both the source job and the ganged job.
• The percentage of the media used by each source job is automatically calculated and listed in the history entries. Note that the percentage is calculated on the basis of the number of pages on the sheet, not on the surface area of the pages.
  Note: A detailed report of ganged material usage by source job is available with Prinergy Business Link software.
• On refine, each page is tagged so that if you copy it to a different location before ganging it, the source job and source page can still be identified when it is imported into Prinergy in a ganged imposition.
• Custom fields can be added to page aliases. Adding a custom field to a source page adds the custom field to the alias. Adding a custom field to an alias adds the custom field to the source page.

Note: Making changes to a page alias, such as re-refining or changing page geometry, also affects the original page.

Identifying page aliases

In the source job, identify:

• Source pages by the icon
• The page aliases for a selected source page in the Get Info dialog box, in the Jobs with alias of page list

In the ganged job, identify:

• Page aliases by the icon
• The source job of a selected page alias in either of the following locations:
  • In the Pages view, in the Pages pane, in the Source Job column
  • In the Get Info dialog box, in the Source Job list

Limitations
Page aliases are not available for:

• Pages that are re-refined after ganging—If you re-refine a page after it has been ganged, but before the ganged imposition has been imported, the ganged imposition will fail to import into Prinergy. Therefore, ensure that page content is stable before ganging.
  Note: Some changes, such as changes to the number of inks or geometry changes, may invalidate the existing ganged imposition. In this case, you will likely need to rebuild the ganged imposition.
• Job archive, purge or retrieve—If you archive a ganged job, the orginal PDF pages are copied and archived. If the ganged job is retrieved, the pages are not linked to the original job.
• Job export—If you export a ganged job, the original PDF pages are copied and exported.
• Versioned jobs—If you gang versioned pages, the original PDF pages are placed in the imposition.
• Copy job (to another server)—When a ganged job is copied to the same server, page aliases are maintained. However, if a ganged job is copied to another server, the original PDF pages are copied and added to the job. 
  • Note: due to PRINERGY-49619, this feature is not currently working with jobs resulting from a copy job action. Please see Known Bugs and Limitations for more information.
• Other imposition software—If you use imposition software other than Preps to gang pages, page aliases may not be created. Using non-Preps software to build ganged jobs and aliases has not been tested. The pages assigned to the impositions may be registered as input files, and may require refining.
• Impositions populated within Prinergy—If, without using Preps, you add more than one instance of a page to an imposition within Prinergy, the pages are duplicated in the imposition.

Note: Prinergy now allows aliases and source pages to have different file names. This enables you to take a copy of the PDF from the subpages folder and put it in another folder, give the copy a new name, and create a layout job ticket that references the renamed copy.