Working with an older Word document is cinchy: Simply open the document in Word 2016. You see the text [Compatibility Mode] after the filename at the top of the window. This text is a big clue that you're using an older Word document. Another clue is that a lot of Word's features, such as the capability to preview format changes and document themes, don't work when you edit an older document.
Microsoft Word has been around for ages. It's used the same doc file format since the early days, back when Word ran on steam-powered computers that took three people to hoist onto a table.
In 2007, Word changed its document file format. Gone was the doc format, replaced by the docx format. Because a lot of people still use older versions of Word, and given the abundance of older doc files still used and available, it became necessary to work with and convert those older documents.
To update an older document, follow these steps:
Click the File tab.
On the Info screen, click the Convert button.
A descriptive dialog box appears. If not, skip to Step 5.
In the Microsoft Word dialog box, click to place a check mark by the item Do Not Ask Me Again about Converting Documents.
Click the OK button.
Click the Save button to save your document.
Use the Save As dialog box. If you're paying attention, you'll see that the chosen file format is Word Document (*.docx).
The document is updated.
The older document isn't removed when you follow these steps. It lingers, although you can freely delete it.