I'm currently typing up notes in Microsoft Word using the outline mode, but when I try to print this document it loses the outlining format and reverts to the original document:

I'm currently typing up notes in Microsoft Word using the outline mode, but when I try to print this document it loses the outlining format and reverts to the original document:

The generel procedure to print the outline (with headers indented etc.) is to switch to outline view and then select the print function.
However, at least in Word 2010 this might be a bit confusing. When you access the print function you are switching away from outline view and you are also presented with a print preview on the right side of the window. This preview will display the document as if it was printed normally not using the outline. However, when actually printing you still get the outline.
If you want to only print the outline down to a level of your choice you simply have to customize the outline view by hiding lower level items before printing it.
This was driving me crazy, too. Finally I found the way to do it. Instead of using the regular Print command (which switches to regular Print Layout view & shows you a print preview), you need to use the Quick Print command.
Here are a couple ways to access it:
Now - how do you use it? First, set your Default Printer to the printer you want to use. Second, put your document in Outline view and arrange what you want to have shown (i.e., how many levels, etc.). Then press the Quick Print button and presto - it prints out what is on the screen, without switching to the Print Layout, i.e., in the Outline view.
I use a template with the same outline structure but the outline levels I do not want to appear are formatted as "hidden." Then when the outline in the document to be printed changes I copy the entire document (Select All—Copy.) In my print template I replace the out dated text with the copied version using Paste Special "Formatted Text RTF" option.
Outlining format by design will not print exactly what is shown in outline mode. If you want your document to look like what's on the screen when you print it, design it in print layout view (View tab -> Document Views -> Print Layout).
You could put in a table of contents, tied to the headings you have used, then just print the pages which have the TOC on them
The solution posted by @Mokubai is the simplest in Word for Windows version 2106: With the document showing in Outline view, go to the View tab of the command bar and check the box next to "Navigation Pane" in the Show section. The navigation pane appears in the left side of the window. Click on Headings in that sidebar. Right-click on the first (topmost/level 1) heading and choose "Expand all" from the dropdown menu. Click on the triangles next to any sections you want to collapse, if any. Then right-click on the first heading again and select "Print Heading and Content." Voila! The print preview dialog appears and at last shows the outline with indenting, text, and images positioned just as they are on screen. Choose your printer and settings, then click "Print."
Ta for the suggestions. I also wanted to copy only a particular level. Don't know much about styles, so instead tried highlighting the desired level(s) in outline view, then printing, yes, but to One Note as the 'printer'. Need to have the One Note 2013 application in the Office suite to do this, and need to specify ONE Note as the 'printer'.
You can then copy from One Note back into a word file. Handy for flipping chapters or headings about, without worrying about the contents. If you copy the headings in outline view straight across to another Word file, it also drags all the 'descendent' levels with it, which is NOT what is required. Word in effect 'filters' out the undesired levels when it sends them to the 'printer' which is a handy feature.
On another Outline-related matter, I would love to know about an outliner in which you could specify ONE LEVEL ONLY (not all the levels down to say, level 3) to print out. A really good outliner would do this.
Microsoft XPS Writer is the only way I found to print the outline view exactly as it is. It looks like a PDF document but keeps all the formatting without defaulting to the main document. Microsoft XPS Writer is an optional printer.
The best way to print an outline is to apply a different style outline to the document, I believe. In Word 2013: Select All, Multilevel List (Dropdown Menu, under HOME), [select any list with HEADING 1-------, HEADING 2------- following it].