On your iPhone: swipe down from the middle of the screen to reveal the Search icon.On your iPad: tap the Loupe icon to use search.Enable the File Content Search (PDF Expert settings > File Content Search) to be able to run searches to find specific words in the content of PDFs. Once you open the app, you can use File names or Content search.
You can also use Search in your list of Outlines, Bookmarks, and Annotations.
There are several types of Search in PDF Expert: file manager search and search in the opened file.