There are a few different ways that data can be imported into a PDF. Karl has outlined two methods. One using an external app and the other a local data file to load data into form fields, but there is a much simpler mechanism that will work with both Acrobat Reader and Pro, which is to use a form submit. A submit performs an HTTP operation and expects the return data to be in a known data format. The returned data is mapped into form fields on the PDF.
To do this you'll need a server side app to get data from the DB, put it in the correct format, and return is as the HTTP response data.
Here are some helpful links:
https://acrobatusers.com/tutorials/submitting-data/
https://www.pdfscripting.com/public/Form-Data-Handling.cfm
Here is the Acrobat JavaScript reference entry for the submit function:
https://opensource.adobe.com/dc-acrobat-sdk-docs/acrobatsdk/html2015/index.html#t=Acro12_MasterBook%2FJS_API_AcroJS%2FDoc_methods.htm%23TOC_submitFormbc-106&rhtocid=_6_1_8_23_1_105