I originally wrote lengthy instructions using Scribus as seen below. However afterwards, I found using LiberOffice Draw is even easier to edit fields and delete existing stuff at least on my Linux OS. I couldn’t find out how to delete existing stuff using Scribus. Which is why I had to use Gimp to black out areas in the Scribus images below. As with Scribus you need to export as PDF to save. Also in my test if you just click on a line your text will be on that line, you don’t need to adjust the positioning as you might with Scribus.
However later I found it wasn’t so good on some PDFs and I had to use Scribus.
So using Scribus (Ver 1.5.5)…
Open Document
After…I find setting View>Zoom>Fit to Width works best
Click Text button then click to the upper left position of the field you want to type in and hold as you drag box to the size you want.
Adjust box size with resize handles if necessary
Double click inside the box (resize handles disappear) and type in your text.
Click somewhere else…box turns black
Click (or double click if you want to edit contents) text box again…box turns red again with the resize handles
Click inside box…a hand appears allowing you to move the text box if needed for better alignment
Repeat to fill in other fields
Select File>Export>Save as PDF
Change Font size
The text for some fields was too large. And googling helped…a little. However the examples/steps shown didn’t match my version. So this worked in my version 1.5.5
Go to File>Prefrences
Select Item Tools…Not Fonts (as you would assume)
Change Text Size
This didn’t immediately work for me until after I restarted the program!