If you do take into account your working time etc. you might actually consider commercial server-side form filling tool, such as FDFMerge by Appligent (for simple filling, the Lite version would be sufficient). In this case, you won't need to noodle around the PDF, trying to interpret it, and attempting to write something back.
In this scenario, you would export an FDF from the database, which is rather easy to accomplish, as FDF is a simple text file. How it has to look can be found with ease as well, by taking the form, filling it out, and exporting the data as FDF. And then, the rest is "filling out the blanks".
For using libraries to do server-side filling, links have already been provided. Just a note: make sure that you will get a good and functional PDF, by relying on well-reputated libraries.