" in IOS-
It's not possible to do that. For the ms-word url scheme to work, the document must live in SharePoint or OneDrive, stated here You can enable users who are running Office on an iOS device to open and edit files stored in SharePoint or OneDrive from any application, and then quickly return them to the original application when they’re done editing the file.
Thanks for the share. I forgot to mention in the original post that our document is hosted in Sharepoint.
With all other devices, we are able to launch the document in word app and since the word app is already registered with users organization, it downloads the Sharepoint document using the url and is also able to upload the changes back to Sharepoint after the user is done with the edits, With iOS, if the application is opened in chrome/safari browser this works perfectly. However the iOS Pega mobile client app is unable to trigger the word using the same uri scheme..