PDF (Portable Document Format) Documents

History of PDF

• Early 1980's at Xerox PARC: Work on printer description languages for newly invented laser printers.
• Postscript invented.
• Different vendors create incompatible versions of Postscript
• Postscript Level 2 tries to bring unity
• Adobe creates PDF:
• Binary, not ascii
• Proprietary format, not open
• Allows movies, sounds, notes, index terms, and is searchable; not simply text and graphics
• Allows complete layout/font/appearance control, unlike HTML
• Allows document security (see below)
• Allows partial downloads from Web server, because pdf files can be large

Creating PDF Docs

• Acrobat writer + print from any normal app
• Acrobat distiller + postscript
• Acrobat capture + gif, pcx, or tiff image files

Viewing PDF Docs

Printing PDF

Use Acrobat Reader or Exchange or your Web browser to print.

Document Security

A PDF document can be set in Acrobat Exchange to

• prohibit printing

People can view your doc on the Web, but not print it

• require a password to read

Uses RC4 (a secret key encryption algorithm from RSA, Inc.)

• prohibit people from changing/saving document

People can view your doc, but not save it locally (e.g., for pay-for-view)

• prohibit people from selecting text or graphics

People cannot violate your copyright by cutting-and-pasting

• prohibit people from adding notes

Using PDF with HTML

1. Link from HTML doc to PDF:

<a href=http://www.adobe.com/a.pdf>

2. Embed PDF in HTML

<EMBED SRC=http://www.adobe.com/a.pdf>

3. Scale an embedded PDF:

<EMBED SRC=http://www.adobe.com/a.pdf WIDTH=50% HEIGHT=50%>

Modifying PDF with Acrobat Exchange

Functions:

• Add thumbnail sketches of pages in a doc



• Create and edit bookmarks (to produce a table of contents)



• Create and edit links (either to URLs or to other parts of doc)



• Define an article within a doc by drawing rectangles around document text
• Add sounds or movies or other actions to occur when doc is opened or closed
• Edit pages:
• crop, rotate pages
• insert, delete, extract, replace pages
• insert one document inside another document
• insert or move pages using thumbnail sketches
• Edit text:
• change text itself
• add new text within a certain space on a page
• change font, color, alignment with touch-up tool



• Annotate document with "post-it" style notes, or produce summary of notes in a doc

Efficient Transfer of PDF Docs over Web

PDF docs, like postscript docs, are often large -- 100's of Kbytes to Mbytes. Acrobat 3.0 has a way to avoid long file download times.

• Acrobat 3.0 has page-at-a-time downloading.
• Web server sends only the requested page
• In Exchange, PDF doc can be configured to download remaining pages in background
• Page-at-a-time downloads are implemented on servers side by either
• built-in Web server support, or
• special CGI app on server

Return to CS6204 home page.

Last modified on 19 June 1997.

Send comments to abrams@vt.edu.
[This is http://ei.cs.vt.edu/~jwww/courseNotes/pdf/index.html.]