Draw text on all pages of PDF using PDFKit - swift

Question

I'm using the following code to draw text on a PDF Document.This seems to draw the text only on a single page.I'm trying to iterate through each page,draw string on it and finally display the PDF document from the MutableData. How do I draw the string on all pages?
var pdffile=PDFDocument(url: input)
let data = NSMutableData()
let consumer = CGDataConsumer(data: data as CFMutableData)!
for y in stride(from: 0, to: pdffile!.pageCount, by: 1)
{
let page: PDFPage = pdffile!.page(at: y)!
let outputBounds = page.bounds(for: PDFDisplayBox.mediaBox)
var mediaBox = CGRect(x: 0, y: 0, width: outputBounds.size.width, height: outputBounds.size.height)
let context = CGContext(consumer: consumer, mediaBox: &mediaBox, nil)!
NSGraphicsContext.current = NSGraphicsContext(cgContext: context, flipped: false)
context.beginPDFPage(nil)
page.draw(with: .mediaBox, to: context)
text.draw(in:drawrect,withAttributes:textFontAttributes);
context.endPDFPage()
context.closePDF()
}
let anotherDocument = PDFDocument(data:data as Data)
pdfview.document=anotherDocument

Answer 1

The main issue here is that context recreated, for multiple pages we should write into the same context (it manages pages by beginPDFPage/endPDFPage pair).
Here is fixed code. Tested with Xcode 13.4 / macOS 12.4
let pdffile = PDFDocument(url: input)
let data = NSMutableData()
let consumer = CGDataConsumer(data: data as CFMutableData)!
// create common context with no mediaBox, we will add it later
// per-page (because, actually they might be different)
let context = CGContext(consumer: consumer, mediaBox: nil, nil)!
for y in stride(from: 0, to: pdffile!.pageCount, by: 1)
{
let page: PDFPage = pdffile!.page(at: y)!
// re-use media box of original document as-is w/o changes !!
var mediaBox = page.bounds(for: PDFDisplayBox.mediaBox)
NSGraphicsContext.current = NSGraphicsContext(cgContext: context, flipped: false)
// prepare mediaBox data for page setup
let rectData = NSData(bytes: &mediaBox, length: MemoryLayout.size(ofValue: mediaBox))
context.beginPDFPage([kCGPDFContextMediaBox as String: rectData] as CFDictionary) // << here !!
page.draw(with: .mediaBox, to: context) // << original !!
text.draw(in:drawrect,withAttributes:textFontAttributes) // << over !!
context.endPDFPage()
}
context.closePDF() // close entire document
let anotherDocument = PDFDocument(data:data as Data)
// ... as used before