There are several types of Search in Documents: file manager search and search in an opened file.
You can also use Search in the list of Outlines, Bookmarks, and Annotations.
Once you open the app, you can use File names or Content search. Enable the 'File Content Search' option (Documents settings > File Manager > Enable indexing) to find specific words or phrases in the content of files.
You can also sort search results by file type:
Search results are split between folders and you can see the results in the current folder.
The Documents search mechanism uses 'And' logic. When you are looking for an exact phrase in the content of the file, e.g. 'color healing', type the phrase in the search bar. All files where this phrase is mentioned will be displayed in the search results.
Note: Once you open a PDF file from the search results, you will not be redirected to the place in the PDF file where the phrase is located. Tap the Loupe icon inside of the PDF file. The phrase you were looking for will appear in the search bar automatically and you can tap any search suggestion to be redirected to the page where the phrase is located.
You can also use Search in your list of Bookmarks, Outlines, and even Annotations.
Tap the Bookmarks, Outlines, Annotations summary icon on the toolbar of the file, then swipe down to reveal Search and quickly find the information you are looking for.
Documents allows searching songs by metadata: a track title, artist, album name or even genre.
Note: Indexing should be enabled in Documents settings > File Manager section.