You can republish a DITA map on a portal server to update the content.
If you have already published a map on a portal server, and the map or its associated files on the repository are modified, you can update the publication on the portal server. Select the same DITA map from the repository, and issue the Publish to Astoria Portal command, specifying the same Publish Location and Publish Name as the existing published map. If the existing published map was created using a snapshot label, select the same snapshot label in the Filtering option. The map and its associated files are updated on the portal server.