Hello Shishir,
Hope you're doing well.
According to your original post, your first error was something like "cordova.plugins.SitewaertsDocumentViewer is undefined".
Like João said, this error happens when a new plugin is not installed in your builds, therefore you'll need to regenerate your builds and install a newer version of your application that contains the new plugin.
Now, according to the image in your last post, it seems to be a different problem: "Cannot read property 'viewDocument' of undefined", which probably means that you are trying to access viewDocument property of a variable that has been declared but it doesn't have an assigned value (undefined). So if you try to access a property of that variable, it will automatically throw an exception (cannot read property of undefined).
Look at this example that may help you to understand. If I try to access length property of an undefined variable, it will raise an exception "Cannot read property 'length' of undefined".
So I'd say that most likely your error is an applicational error, probably related on how you are implementing your client actions and the JavaScript associated to them.
Anyway, as I can see, you are trying to use a plugin in order to display a PDF file. Maybe you would like to consider the usage of File Viewer Plugin for that purpose :)
This plugin is already implement, meaning that the client actions are ready to be used. You could use OpenDocument client action to show your PDF file.
You can follow this thread with an implementation of this plugin where the objective was to show a PDF file: https://www.outsystems.com/forums/discussion/66476/file-plugin-and-file-viewer-plugin-on-android-device/
Hope that this helps you!
Kind regards,
Rui Barradas