Problem submitting pdf form online

Hi, I am trying to submit a pdf form to HMRC online and it is being rejected because of issues with validating signatures via signature panel. I have followed through the fix suggested by HMRC but it has not worked. It says it works for Adobe Acrobat version 11 but I can't find which version I have. The browser is supposed to show it but it does not. Can anyone suggest how to find out the version and/or solve the problem?