When a PDF Form is shown in Workspace, the LC server actually attempts to make a modification to the form (called "augmentation") in which a scripting bridge is added to the form. This happens inside the Render Service used to show the form. Workspace needs this to happen so that it can instruct Acrobat/Reader in the browser to hide the submit button, thus allowing the Workspace UI buttons to be used instead. I know that if the PDF Form is signed then LC will not attempt to make this modification in case it breaks the signature. This is what might be happening here because when you reader extend a PDF there is actually a signature applied.
If this is the cause I can think of two suggestions off hand:
- You might consider Reader Extending the Form on demand as part of your render service by uploading your Reader Extensions Credential (the p12 / .PFX file) to Trust Store and then using it with the Reader Extensions Service in a new version of your render service.
- You can use LC Designer to add the "Form Bridge" to your form before you reader extend it with the web application and place it in your repository.