Scope: Word 97 - Word 2019 / 365 (and later)
Word comes with a ton of Keyboard Shortcuts built-in. Here is a page discussing them as well as the Alt key shortcuts for maneuvering the commands in the Ribbon. Keyboard shortcuts in Word - Office Support
That article does not discuss all of them, though.
This article is about seeing those and shortcuts that may have been added to your Word program. Here is a support page on how to add your own shortcuts.
This page shows how to find (almost) all of the keyboard shortcuts active in your installation of Word.
The methods discussed here have been discussed since the first Word newsgroups. They are neither new nor secret.
Method 1: A list of (almost) all keyboard shortcuts in your Word Installation:
Bring up a list of your macros using the keyboard shortcut (Alt+F8) or by viewing macros under the Developer Tab.
You actually want Word Commands.
Run that command.
This will bring up the dialog box shown below. You want current keyboard settings.
You will get a fairly lengthy new document with a table showing each command or macro or style to which a keyboard shortcut has been assigned with that shortcut. Here is a sample of what you will see:
The notes as to the source of the commands are NOT in the list.; I added them to the screenshot.
Key assignments to macros are not shown and if a keyboard shortcut has been assigned to a macro and was previously assigned to a command, the command will be shown with the shortcut even though over-ridden by the assignment to the macro.
Method 2: A list of custom keyboard shortcuts stored in a document or template.
The list of all shortcuts includes in its pages any custom shortcuts working on your system except those for macros. Since it does not disclose the source, it is difficult to figure out which is built-in and which is custom.
Word lets you print custom Key Assignments out. In Print What? you have to choose Key Assignments...
Word 2003 Print Dialog
Word 2019 Print Dialog
This printout will show keyboard shortcuts that are in the open document or its template. It also shows, under "Global" those stored in the Normal template.
The printout shows macros to which keyboard shortcuts have been assigned. It may or may not show the macro name. If it does, it will show project.module.name.
It does not show shortcuts that may be active from other global templates - that is, loaded Add-Ins. I recommend you do print to pdf rather than paper. Then print the pdf to paper if you need to.
Here is a screenshot from a pdf produced as a printout:
Method 3: Use Chris Woodman's Keyboard Shortcut Organizer
This does not give you a printout but shows any custom shortcuts that have been added. You can check each document and template using this tool.