On SharePoint 2010, there is a useful function called "Add to My Links" to add links to any document. On SharePoint 2013, there are some changes and this function will not work the same way as on previous version. Here is what we found that could help you to educate your users.
Let’s explain how this function works on SharePoint 2010 first. If you enable Portal Site Connection by click Site Settings-> Site collection Administration - > Portal site Connection - > Connect to Portal site and enter valid site for portal site as showed in the following screenshot. The first way you will be able to use the function by click denouement and select "Add to My Links" as indicated in the following two screen shots.
The second you could also use this function by clicking "Connect to Office" from library ribbon to go to My Links page. If this is disabled, you may check this blog to fix it.
On 2013, after enabling the Portal site Connection, you will NOT find the "Add to My Links" for individual document. The only way to access the same function is through "Connect to Office" from library ribbon as in the following screen shots.
Please note the application page on 2013 supports both14 and 15 hive version. The new My Links application page is on 15 hive as in the following screen shot.
Now, you understand how to use "Add to My Links" function on SharePoint 2013. Now, you should understand why Microsoft remove the access this function directly from document. There are two major reasons Microsoft wants to replace this functions on 2013.
The fist reason is Microsoft recommend using the social tag to category documents so you could search them easily. See the screenshot.
The second reason is 2013 has new function and you could display important links graphically using Promoted Links web part. The web part can be added to anyway to share the links. See screenshot for details.
Since 2013 has provided many new functions and you should looked at these functions before upgrade.