MS Word > PDF: Retaining custom page size

It took me ages to figure out and many articles on here pointed me in the right direction but didn't quite work for me.

I use Word 2016 for Mac and Abode Acrobat Reader DC.

To create a PDF that retains the custom page size:

1. Highlight all of the text in the MS Word document.
2. File > Page Setup> Page Attributes drop down box, choose Microsoft Word.
3. For the 'Apply page setup setting to:' field, select 'Selected Text'
4. Then immediately go to File > Print
5. Click on 'Copies and Pages' drop down box and select 'Paper Handling'
6. Select 'scale to fit paper size'
7. Choose ‘Custom’
8. Then click on PDF (bottom right hand corner)
9. Click Acrobat Reader (if installed).
10. To check that it has worked, open the document in Adobe Acrobat Reader.
11. File > Properties
12. It should say at the bottom in the Advanced section what the page size is.
13. To change the page size from inches to mm, click on Acrobat Reader at the top next to File.
14. Go to Preferences > Units.