Update pdfio.md

doc/pdfio.md

@@ -138,6 +138,76 @@ Understanding PDF Files
 A PDF file is structure in a way, so that it would be displayed in the same way 
 across multiple devices and platforms. The basic structure of PDF File is as follows:
 
+### A small PDF File
+The following is a PDF which says "Hello, World" on one page:
+```
+%PDF-1.0                            **Header starts here**
+%âãÏÓ
+1 0 obj                             **Body starts here**
+<<
+/Kids [2 0 R]
+/Count 1
+/Type /Pages
+>>
+endobj
+2 0 obj
+<<
+/Rotate 0
+/Parent 1 0 R
+/Resources 3 0 R
+/MediaBox [0 0 612 792]
+/Contents [4 0 R]/Type /Page
+>>
+endobj
+3 0 obj
+<<
+/Font
+<<
+/F0
+<<
+/BaseFont /Times-Italic
+/Subtype /Type1
+/Type /Font
+>>
+>>
+>>
+endobj
+4 0 obj
+<<
+/Length 65
+>>
+stream
+1. 0. 0. 1. 50. 700. cm
+BT
+/F0 36. Tf
+(Hello, World!) Tj
+ET
+endstream
+endobj
+5 0 obj
+<<
+/Pages 1 0 R
+/Type /Catalog
+>>
+endobj
+xref                          **Cross-reference table starts here**
+0 6
+0000000000 65535 f
+0000000015 00000 n
+0000000074 00000 n
+0000000192 00000 n
+0000000291 00000 n
+0000000409 00000 n
+trailer                       **Trailer starts here**
+<<
+/Root 5 0 R
+/Size 6
+>>
+startxref
+459
+%%EOF
+```
+
 ### Header
 This is the first line of a PDF File. This specifies the version of PDF Format used.
 - Example: '%PDF-1.0'