When trying to digitally sign a pdf in Adobe Acrobat Pro 9 I get the following error information:
" The Windows Cryptographic Service Provider reported an error:
Provider type does not match registered value.
Error Code: 2148073499"
Please refer and try the troubleshooting steps from the following KB docs which discusses the similar issue Signature creation error when you sign a PDF (Adobe Acrobat 8, 9 on Windows)
Note: Acrobat 9 is declared as an End of support product, for more information refer to End of support | Reader 9 and Acrobat 9 (and earlier)
Hope this helps and let us know how it goes.