I'll assume we are talking about Windows O.S. and with Batch tag you will reffer to batch-processing instead of Batch lang, anyways I'll advise that Batch is a limited language that only covers basic common system based tasks, it is not intended to read a non-plain text file such a PDF, it can't.
To read an specific format like a PDF an external parser/interpreter is need.
There is a good C# based solution that demonstrates how to read the data contained in a PDF in a human readable way:
It uses iTextSharp library, which is open-source:
Alternatively, here is an VBS based solution from the Adobe user guide, it needs the COM objects installed from Adobe app.
Note the chapters where you are interested for this task:
To assist you a little bit in VBS, here is an VBS script question that could helps you:
Dim accapp, acavdocu
Dim pdf_path, bReset, Wrd_count
'AcroExch is acrobat application object
'Need to create one AVDoc object par displayed document
'Opening the PDF
If acavdocu.Open(pdf_path,"") Then
bReset=1 : Wrd_count = 0
'Find Text Finds the specified text, scrolls so that it is visible, and highlights it
Do While acavdocu.FindText("Invoice#", 1, 1, bReset)
bReset=0 : Wrd_count=Wrd_count+1
'Wait 0, 200
msgbox "The word 'Invoice#' was found " & Wrd_count & "times"
Set accap=nothing : Set accapp=nothing
But I'll advise apparently it seems don't work as expected, I taken it from this site: