Which endpoint are you trying?

Please send me a private message with the name of your organization and location thanks

I am not able to attach xdp and xml fileExport data from the pdf using acrobatopen the address1.pdf in designer and save it as xdpthen use the xml and xdp to generate the pdf using the workbench process. it should work

https://forms.enablementadobe.com/content/forms/af/from1040.html fill in some details, then click on the View PDF and then on View PDF check box to see the pdf populated with your data

what is the version of AEM Forms? is this a custom endpoint?

Did you stop the server before creating the install folder and copying the far file?

I have written a tutorial on saving and prefilling forms with data and attachments in the Azure portal. This approach is only supported for forms based on Core ComponentsLet us know if you have any questions on this tutorial

If you are using AEM forms6.5, you will have access to assembler service. you will need to be familiar with assembler service and creating DDX documents https://helpx.adobe.com/pdf/aem-forms/6-2/ddxRef.pdf 

Have you looked at watermarking capabilities using assembler services in AEM forms?

Try passing in the xdp template instead of the pdf