Click the Start button at the top-left of the screen to expand the Spelling Inspection panel. 

Selecting the language

Click on the desired language(s) in the Language(s) field to compare the file against one or more standard dictionaries. 

Inspecting multi-page documents

If a multi-page file is loaded, the Select Page(s) field appears. Click on the desired page to select it for inspection.

There is no limit to the number of pages that can be inspected, but larger amounts of pages take longer to inspect.

Inspection may start!

Click Inspect once the language and page(s) are set.