@Pushpalatha 

kindly try out below options:

I think the docman dll’s are not downloaded properly. Did you try closing the IEE and open it again.

Try it on a different machine with correct .NEt framwork versions installed. 

Go to document revision window do you see dll files are getting downloaded. small dialog box in your right bottom screen. 

do a click once cache clear

https://social.msdn.microsoft.com/Forums/windows/en-US/c554c98c-f87b-4e51-ba08-5e5a514e5d3b/clear-clickonce-temporary-files?forum=winformssetup

From where do you open the document? As @Sahan Udana says, it looks like the Docman DLL is missing. Is Docman properly included in the build?

@Mathias Dahl 

Yes application was accessible till last sunday and DLL’s were properly included. I am trying to open the document from screen Prepare Work Order. When i try to navigate between tabs also am getting same error. 

Okay, thanks! I cannot say what has gone wrong I'm afraid. Someone, or something, has managed to make one or more dll files missing.

Hi,

Did a recent a delivery/installation done to this environment? There were some situations in the past  the dll may got corrupted during the installation. 

regards,

Sahan