In rare instances, users may experience that they are unable to save overlays, even if this is a simple case of removing a single automatically generated link and not actually adding any to the publication.
The cause of this error message in the overlay editor can be due to either an erroneous PDF or Overlay link (more likely the latter).
Method 1 - Check the PDF for errors or faulty links
Embedding links within PDF files is a common practice for companies who produce digital content, however many who source advertising pages or content from third parties often overlook the possibility that the content has corrupt links, whether broken or characters that are not recognised by the computer or the YUDU system.
To check any suspect links, open Adobe Acrobat and using the select tool 
hover over an area that is linked, such as below:
Should the link contain suspect characters, be corrupt or you wish to change, simply click the Tools menu on the right, then select Add or Edit Link (Acrobat XI):
Save and reupload the PDF to overwrite the original to remove the previous version.
Method 2 - Replace previous overlays on the page
Similar to the issue encountered above, corrupt URLs or incorrect page links can cause the save failed prompt to appear and therefore it is suggested that users check any suspected URLs in the overlay editor. An example of a potentially corrupt URL is shown below:
The same is apparent for page links when pages are frequently added and removed, specifically when a link to a page is made, then the destination page is removed.
For page links, removing the links on the page then re-applying them will remedy the issue.