PostScript PDF (1.7), manually writing code

Question

I'm trying to manually write a simple PDF file that contains a title, some text, and an image. I found one example of a manually written "Hello world" and managed to change some things, but I cant get it working for another text object. I have looked for help on the internet but with no luck, I guess not many people write their own PDF files.

This is what I have so far:

%PDF-1.7



1 0 obj  % entry point
<<
  /Type /Catalog
  /Pages 2 0 R
>>
endobj



2 0 obj
<<
  /Type /Pages
  /MediaBox [ 0 0 200 200 ]
  /Count 1
  /Kids [ 3 0 R ]
>>
endobj

3 0 obj
<<
  /Type /Page
  /Parent 2 0 R
  /Resources <<
    /Font <<
      /F1 4 0 R 
    >>
  >>
  /Contents 4 0 R
>>
endobj


4 0 obj  % page content
<<
  /Length 20
>>
stream
BT
80 180 TD
/F1 14 Tf
(PDF) Tj
ET
endstream
endobj

5 0 obj  % page content
<<
  /Length 20
>>
stream
BT
50 70 TD
/F1 14 Tf
(this is a pdf) Tj
ET
endstream
endobj


trailer
<<
  /Size 6
  /Root 1 0 R
>>
startxref
492
%%EOF

I have tried adding another text object with "this is a pdf" text but it wont show up, I don't know what could be wrong, I tried changing a few things but with no luck. The image part I don't have it either, so some help with that would be nice.

This is a wiki about the "hello world" pdf I found: http://www.gnupdf.org/Introduction_to_PDF

Adobe offers some explanation on how the pdf works but I cant find anything that would fix my problem: http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf

Answer 1

This is not a valid PDF. If Acrobat opens it at all it's because it's given up on the xref table and done a full scan of the file, but your PDF is invalid. 4 0 obj is not a font, as you specified, and 5 0 obj is not accessed from anywhere.

PDF specification requires an xref table which points to the exact position in the file for each object. You can't realistically write this by hand unless you intend to manually update the entire xref table every time you add or remove even 1 byte from the file.

You can write a PDF from scratch like this from code easily enough but it will not work to just open a PDF in notepad and start changing things because the index (xref) immediately becomes corrupt.

I'd also advise against putting comments throughout the file unless the comments start on new lines. Otherwise some PDF parsers will get confused as this is generally not expected. Usually PDF files do not contain comments (with the exception of the second line, which is recommended by Adobe to be a comment of some non-ASCII characters so FTP recognizes the file as binary) seeing as they are virtually impossible to write manually anyway.

http://www.adobe.com/devnet/pdf/pdf_reference.html

Answer 2

A few years ago, I wrote a book which covers exactly this sort of thing:

http://www.amazon.com/PDF-Explained-John-Whitington/dp/1449310028/

No free online version, I'm afraid. You can get all the same information from Adobe's own documentation, which is free, but it's a rather long document!