Comment by 1vuio0pswjnm7

Below is a PDF. It is a .txt file. I can save it with a .pdf extension and open it in a PDF viewer. I can make changes in a text editor. For example, by editing this text file, I can change the text displayed on the screen when the PDF is opened, the font, font size, line spacing, the maximum characters per line, number of lines per page, the paper width and height, as well as portrait versus landscape mode.

   %PDF-1.4
   1 0 obj
   <<
   /CreationDate (D:2025)
   /Producer 
   >>
   endobj
   2 0 obj
   <<
   /Type /Catalog
   /Pages 3 0 R
   >>
   endobj
   4 0 obj
   <<
   /Type /Font
   /Subtype /Type1
   /Name /F1
   /BaseFont /Times-Roman
   >>
   endobj
   5 0 obj
   <<
     /Font << /F1 4 0 R >>
     /ProcSet [ /PDF /Text ]
   >>
   endobj
   6 0 obj
   <<
   /Type /Page
   /Parent 3 0 R
   /Resources 5 0 R
   /Contents 7 0 R
   >>
   endobj
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   <<
   /Length 8 0 R
   >>
   stream
   BT
   /F1 50 Tf
   1 0 0 1 50 752 Tm
   54 TL
   (PDF is)' 
   ((a) a text format)'
   ((b) a graphics format)'
   ((c) (a) and (b).)'
   ()'
   ET
   endstream
   endobj
   8 0 obj
   53
   endobj
   3 0 obj
   <<
   /Type /Pages
   /Count 1
   /MediaBox [ 0 0 612 792 ]
   /Kids [ 6 0 R ]
   >>
   endobj
   xref
   0 9
   0000000000 65535 f 

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