I need the ability to sign the documents external. By export the hash to be signed and send it outsource (Mobile App, external server). And then receive the signed hash to be added to the document.
Can your solution do that? Do you have a sample code in .Net C# ?
Aspose.PDF for .NET API supports signing a PDF file using a smart card as well as a certificate. However, we are afraid that signing with an external HSM may not be available at the moment and we need to investigate this possibility. You may visit below documentation articles for your kind reference.
Please share some more details about the server e.g. Azure KeyVault so that we can log an investigation ticket and share the ID with you.