By following the easy guides below, you will get information on how annotations and links, as well as attachments, work in PDF.

Links and attachments in PDF files

In Adobe Acrobat

1. Create a link using the Link tool
Choose Tools > Edit PDF > Link > Add or Edit.
 
2. The pointer becomes a crosshair (+), and any existing links in the document, including invisible links, are temporarily visible. Drag a rectangle where you want to create a link. This is the area in which the link is active.

3. In the Create Link dialogue box, choose the options you want for the link appearance.

4. Select one of the following link actions:
 
5. Go To A Page View
Click Next to set the page number and view magnification you want in the current document or in another document (such as a file attachment), and then click Set Link.
 
6. Open A File
Select the destination file and click Select. If the file is a PDF, specify how the document should open (for example in a new window or within an existing window), and then click OK.
 
Note:
If the filename is too long to fit in the text box, the middle of the name is truncated.
 
7. Open A Web Page
Provide the URL of the destination web page.
 
8. Custom Link
Click Next to open the Link Properties dialog box. In this dialog box, you can set any action, such as reading an article, or executing a menu command, to be associated with the link.

You can read the entire guide at Adobe:
https://helpx.adobe.com/acrobat/using/links-attachments-pdfs.html

Overview of the hyperlinks panel

You can create hyperlinks when exporting to Adobe PDF or SWF so that the reader of the document can click a link and go to other pages in the same document, to other documents, or to websites. Hyperlinks that you export to PDF or SWF in InCopy are not active.

A source can be a hyperlinked text, a hyperlinked text frame, or a hyperlinked image frame. A target is the URL, file, email address, text, anchor point, or shared target to which the hyperlink leads. A source can only lead to one goal, but an unlimited number of sources can lead to the same goal.

Please read the entire guide at Adobe:
https://helpx.adobe.com/se/indesign/using/hyperlinks.html