Putting data into existing PDF

I have had to introduce data for NGO into an existing PDF. Why PDF ? Because yes, it is easy to print. but from a templating point of view it is a nightmare.  by templating I understand putting data at specific places , like

First Name :

Last Name :

And filling in the blanks.

The solution: complicated.  The  pdf can have Form fields to be filled . I discovered

 https://www.pdfescape.com/windows/

that can be used to put form fields into existing documents and save the pdf.

And I figured that this is all. Nope. Look here

109 0 obj
<</Subtype/Widget/Rect[119.52 347.25 565.92 358.77]/AP<</N 110 0 R>>/DA(/Helv 8.64 Tf 0 g)/F 4/FT/Tx/P 1 0 R/T(untitled22)/Q 0/V(*NumeONG*)>>

endobj

110 0 obj
<</Type/XObject/Subtype/Form/BBox[0 0 446.39999 11.51999]/Resources<</Font<</Helv 77 0 R>>>>/Filter/FlateDecode/Length 90>>stream
xœÓ©Ppòuær
á2PIå\†@ª
ÈNñ‹¸ô=RsÊ,ôÌLBÒ¸€ÐPÁHÁHÏÌL!$—+ZC˯47ÕßÏ]K36Ä‹Ë5„Ëh&endstream

endobj

The PDF format is a primitve form of XML. The 109 0 obj  finishes with  endobj . I figured that I will replace
*NumeONG*

with the name and all will be ok. Nope . The critical point is the stream at the next obj

110 0 obj
<</Type/XObject/Subtype/Form/BBox[0 0 446.39999 11.51999]/Resources<</Font<</Helv 77 0 R>>>>/Filter/FlateDecode/Length 90>>stream
xœÓ©Ppòuær
á2PIå\†@ª
ÈNñ‹¸ô=RsÊ,ôÌLBÒ¸€ÐPÁHÁHÏÌL!$—+ZC˯47ÕßÏ]K36Ä‹Ë5„Ëh&endstream
endobj

Not only is is encoded

Filter/FlateDecode

but also it says the length of the stream,

Filter/FlateDecode/Length 90

That is a problem, because the replacement for the name will be dynamic.

Solution?

The qpdf solftware http://qpdf.sourceforge.net that allows to transform those streams into something readable

qpdf –qdf  –object-streams=disable   m.pdf a.pdf