Add extra text input for file field For Drupal 7, in page content type there is a multiple file upload section. Description is enabled for the file upload, but I need to add one more text input for each images to ask user enter the year file belongs to. 

I am not very good at Drupal. So if I can find a clear solution it will save my day. Thank you from now.
I would recommend using the field collection module instead. Create a field collection with a file upload field, description field and file owner field (can be a text field or user reference field. Set the field collection to unlimited. Then add the field collection to your page content type. It will allow you to do more custom things moving forward.

https://www.drupal.org/project/field_collection 
https://www.drupal.org/project/references