How to automatically link LaTeX .bib references to a set of pdf full-text articles?
Here is one nearly automatic way to do it using Zotero (https://www.zotero.org/):

1) import the PDFs in Zotero. One way is to select multiple PDFs and drag them into a collection (in the LHS pane) of Zotero.

2) Select the PDF items (CTRL click in Windows for multiple selections), right click and select "Retrieve metadata from PDF". Note that this step searches online databases for missing information and seems fairly robust.

3) import the .bib file in Zotero

4) Go to the duplicates collection in the LHS panel and merge all the duplicates.

Issues:

1) In step 4, there may be false negatives if the automatically retrieved metadata (in step 2) is too different from the corresponding entry in the .bib file (step 3)

2) Step 2 might fail on old scanned PDFs.