How to get Preview to open links to local files?

Preview is neither a PDF Editor, nor does it offer link annotation that afixes a file URI link on text. By file URI, I mean the following format:

file:///Users/yourname/Desktop/any.pdf



You can use Apple's Pages to create a new, or open an existing document, and associate a file URI with selected text to receive the link information. Tested in Pages v8.2.1 on macOS Mojave 10.14.6.

1. Select the text and underline it in black
   1. For a color underline, press ⌘+T to expose the Font panel.
   2. The toolbar item to the right of the gear icon is for underline.
      1. Click the underline toolbar, from its menu, choose Color
      2. From the color chooser, select the color for your link underline
      3. Then, select Single from the Underline menu to apply that underline color
2. Press ⌘+K to open the Link Editor, Webpage, and type your file URI in the Link text field. Press return when done, and then Escape key to dismiss the link editor.
3. Export the Pages content to PDF.
4. Single-click the underlined link in the PDF to open the file URI target in a new Preview window.

WIth a paid PDF Editor, one can do all of the above in an opened PDF and directly assign the link there.

By default, non-underlined text in Pages will create an invisible link in the PDF that you cannot detect unless you pass your mouse over it.

On macOS, the only means to link from a parent PDF to another PDF elsewhere on the local filesystem in Preview — is by an explicit, full file URI path designation. Relative addressing simply is not supported. You would use an https URI for a PDF on a remote server if you did not want static parent PDF location issues.