you can not use a PDF/Word doc as a view directly (though you can display in an iframe if supported by the browser).
You can download file of type PDF/WORD, then upload to the server and process.
If you use word, you could implement WEBDAV support (an http file protocol supported by word), so you could edit directly in word. On WEBDAV saves, you would inspect the word file to see if the form was filled in.
for either of these solutions, you need to pick a library that allows processing of PDF forms, or word files.
you can write a PDF viewer application, (this is companies like docusign did), that supports form entry. This is probably a much larger project.
but it would need to a pretty large form for these projects to less work.