PDF Expert 7 offers multiple types of search:
On iPad, tap the search field at the top left and type your query.
On iPhone, swipe down from the middle of the screen to reveal the search icon. Tap it to start searching.
At the top of the keyboard, you can select a particular file type to search for:
PDF Expert 7 shows the results from the current folder at the top.
Note: Once you open a PDF from the search results, you won’t be redirected to the page with the word you searched for. Tap the search icon inside the PDF file. The phrase you were looking for will appear in the search field automatically so you can quickly jump to the page with the needed word.