Original article from PrintUI can be accessed here.
Packaging failures can come from a variety of problems. The first place to look, of course, is in the error messages inside the PrintUI Management panel in InDesign. If there is an error message, that's something that needs to be taken care of in your layout before you can proceed.
· A common problem is using linked files located on network drives. If this appears to be the case (you might see a warning regarding missing links, for example, but the InDesign Links panel does not report any problems), there are two ways to work around it in InDesign. The first is to open the Links panel and select all of the links, then from the panel's flyout menu choose Utilities > Copy Link(s) to Folder... and choose a folder on your local hard drive. This will copy the selected links from their various locations and collect them into a single folder, and simultaneously relink to the new folder location.
The second method is to run File > Package... from within InDesign and pick a location on the local hard drive. By default this will copy the .indd file, the links, and fonts (except Chinese/Korean/Japanese) into a single folder and update the links in the copied file to point to the new links folder. You can then open the .indd file from the package and you should be able to proceed to upload.
· The next common cause of packaging failure is the use of pasted or embedded images and graphics. PrintUI does not allow pasted images and you should receive a Preflight warning, but content pasted from Illustrator may slip through. The complexity of pasted Illustrator content will determine how it is handled by InDesign, which in turn will affect how it works in PrintUI. If the object becomes editable paths in InDesign it will probably be OK, an embedded .eps file will not.
InDesign also allows you to embed a placed file so it is no longer linked. There is virtually no reason you would want to do this, however, as it means your .indd file now also contains all of the extra data that is the embedded image. If the object appears in the Links panel PrintUI will attempt to extract it before packaging.
· Third-party plugins can occasionally cause a problem with packaging or output from an uploaded template (XMPie is one known example). If you have third-party plugins installed, and are experiencing a packaging problem, disable the plugin temporarily, export your file to .idml, open that and resave. This should strip out the plugin information and allow the packaging to proceed. Test your uploaded template thoroughly.
· Use of other unsupported methods or object types can also lead to packaging problems. There is a list of Known Issues available if you click the "?" icon in the lower right of the PrintUI Management panel to open the Help screen. This list hasn't been updated in some time, and many of those things are now supported, either fully or partially, and some will work in your template when they are on the non-editable Background or Foreground layers even if they won't work as editable objects, but you should test your templates thoroughly, including making PDFs from them, after uploading if you choose to try this. PrintUI cannot provide technical assistance for problems you might encounter with the use of objects or methods that are unsupported.