Do you want to deploy a set of changes, or create a self-contained application? Choose a development model.
Once you have deployed the repository to your target org, navigate to your desired Lightning Page and use the gear wheel, then select Edit Page. Under Custom, drag and drop the pdftronWebViewerDiffContainer onto your desired Lightning Page, click Save and make sure the page is activated under Activation.
Use the search bar to look for files (keep in mind you can only search files that you have access to). When you have selected two files, you can click Compare and the files will load up side by side in WebViewer with highlighted diffs like so:
