from PyPDF2 import PdfReader, PdfWriter

from reportlab.pdfgen import canvas

from reportlab.lib.pagesizes import letter,A0,A4,landscape

from decimal import Decimal

from reportlab.pdfbase import pdfmetrics

from reportlab.pdfbase.ttfonts import TTFont

import io

# if you dont have admin rights you need this line of codes, change UserName with you user name #import sys #sys.path.append("/tmp/TEST") #c:\users\UserName\appdata\local\programs\python\python39\lib\site-packages

pdfmetrics.registerFont(TTFont('Vera', 'Vera.ttf'))

pdfmetrics.registerFont(TTFont('VeraBd', 'VeraBd.ttf'))

pdfmetrics.registerFont(TTFont('VeraIt', 'VeraIt.ttf'))

pdfmetrics.registerFont(TTFont('VeraBI', 'VeraBI.ttf'))

draw the text

def drawText(packet,width,height,text,textsize):

c = canvas.Canvas(packet, landscape(pagesize=A0))

c.setFont('Vera', textsize)

c.translate(0, 0)

c.translate(width, height)

c.rotate(45)

c.drawString(0, 0, text)

c.save()

Function to add text to an existing PDF

def add_text_to_pdf(input_pdf, output_pdf, text):

# Read the existing PDF

reader = PdfReader(input_pdf, strict=False)

writer = PdfWriter()


# create a new PDF with Reportlab

packet = io.BytesIO()

packet.seek(0)


# read your existing PDF

existing_pdf = PdfReader(input_pdf, strict=False)

output = PdfWriter()


# add the "watermark" (which is the new pdf) on the existing page

for i in range(len(existing_pdf.pages)):

    page = reader.pages[i]

    width = float(page.mediabox.width)

    height = float(page.mediabox.height)

    # actual size of the pdf file

    lox = 0.5*float(page.mediabox.width)*25.4/72

    locy = 0.5*float(page.mediabox.height)*25.4/72

    #print(width,height)
    #print(2*locx,2*locy)

    textsize=width/25 # text size relative to width of pdf

    drawText(packet,0.5*width-50, 0.5*height-50,text,textsize)

    new_pdf = PdfReader(packet)

    page = existing_pdf.pages[i]

    page.merge_page(new_pdf.pages[0])

    output.add_page(page)


# finally, write "output" to a real file

outputStream = open(output_pdf, "wb")

output.write(outputStream)

outputStream.close()

Example usage

add_text_to_pdf("testplan2.pdf", "testplan2_modified.pdf", "Draf Plan")

add_text_to_pdf("testplan3.pdf", "testplan3_modified.pdf", "Draf Plan")

print("finished")