If your computer is Windows (any version), open the Telephone Directory PDF file with your default PDF reader and use the keyboard shortcut Ctrl + F. Hold the Ctrl key down and tap the F key. A search box will open. Enter the name you are looking for and press Enter.
There's a quick and easy keyboard shortcut you can use to search for words on your Mac. Open the Telephone Directory and use this command, Command + F. It lets you search for words in everything from documents to web pages. Alternatively, you can use the search bar in Preview to search through text-based documents on your Mac.
If you can't open the telephone directory, get Adobe Reader. It can be downloaded for free by going to https://get.adobe.com/reader/ in a web browser and clicking Download Now. It is available for Windows and Mac.
Save a copy of the Telephone Directory on your Desktop for quick lookups. Having a copy in your cell phone can also be handy.