Summarize:

Double-clicking the PDF will accomplish this if Adobe Acrobat is your computer's default PDF reader. If Adobe Acrobat isn't your default PDF reader, do the following:   Windows — Right-click the PDF file, select Open with, and click Adobe Acrobat.  Mac — Click the PDF, click File, select Open With, and click Adobe Acrobat. It's a menu in the upper-left side of the screen. A drop-down menu will appear. On Windows, you may first have to click the View tab at the top of the Acrobat window and then select Tools. It's near the top of the page in the "Create & Edit" section. This opens the editing toolbar and additional options at the top of the window. It's next to the icon of a chain in the editing toolbar at the top of the page. This opens a drop-down menu. It's the first option at the top of the drop-down menu. Doing so turns your mouse cursor into a crosshairs icon. Click and drag your mouse cursor over and down across the text or the object that you want to use as a hyperlink, then release the mouse button. Doing so will open a window. For example, if you wanted to add a link to the words "Click here:", you would drag from the top-left side of the "C" in "Click" to the bottom-right side of the "e" in "here". Select the "Link Type" drop-down box and choose whether or not you want the clickable rectangle you just selected to be visible or invisible. If you choose a visible link, you can select:   Line Style: Set the type of outline you want the box to have; solid, dashed, or underlined.  Color: Choose what color you want the outline to be.  Highlight Style: Set what you want the linked box to do when clicked (only applies to certain PDF viewers). This will depend on the type of link you want to add:   Go to a Page View: Links to another page in the PDF. Click Next, go to the page you want to select, then click Set Link.  Open a File: Select a file from your computer, click Select, fill out any necessary options if prompted, and click OK.  Open a Web Page: Enter the address for the website you want to link (making sure to use the website's full address, including "https://") then click Enter. Press Ctrl+S (Windows) or ⌘ Command+S (Mac) to save your changes to the PDF. The linked item should now be active as a hyperlink, meaning that you can click it to open the link.
Open the PDF in Adobe Acrobat. Click Tools. Select Edit PDF. Select Link. Click Add/Edit Web or Document Link. Create a link. Choose the link's appearance. Select the link's action. Save your PDF.