[pdftex] Fonts

[Michael Chapman]

On Monday 31 March 2003 1:20 pm, John Culleton wrote:
> On Sunday 30 March 2003 07:11 pm, Reinhard Kotucha wrote:

> > And the question is:
> > Does the PDF spec allow to set a flag that says that printing is
> > discouraged?  That would be a little bit useful, though not safe at all.
>
> In answer to the last question, yes it does. It is called a copyright
> notice
>
> :-)
>
> The quality of the screen display is limited by the screen dpi. So if one
> should
> capture a page from the screen, edit out the borders, and print the results
> then the resolution would be the equivalent of 72 or 75 dpi, not the 300
> to 600 dpi expected for ordinary printing on a laser or inkjet printer.

But, for images one can always zoom in on a portion of the page and then do a 
screencapture. So if the object is 'lifting' small images rather than ripping 
the entire text, then resolution is less of an obstacle.

> OTOH if one hacks Xpdf as suggested above the file could be printed at its
> expected resolution.

Yes but the proportion of e-book readers who are "A reasonable good 
C-programmer" is something like 1 in 10^n with, I guess, n >> 4.

(BTW there is one piece of free software, I believe still available, that 
just ignores encryption. Displays the same as Acrobat and Xpdf, but then 
prints regardless ... ... . The 'fact' that that is not that well known, and 
that Derek Noonburg says "I occasionally get email asking if I can explain 
how to crack a PDF file, or if I can help decrypt a PDF file", all seem to 
imply that generally encryption works (to a degree). Quote from 
<http://www.foolabs.com/xpdf/cracking.html>)

> Bottom line, there is no defense possible against a reasonably diligent
> thief. 

I would not agree, well not so much disagree as quibble. I think you need to 
delete "reasonably".
But the same applies to all security. It is a cost:benefit. Not too wonderful 
encryption and trusting Reader-writers to write code that respect content 
authors' concerns has got to be far from perfect, but basically it does work 
(like -for most people, most of the time- locking the door at night).

> Some discouragements I plan to use include:
> 1. An unhandy page size, to make printing the file wasteful.

Size or format ??
Acrobat just allows printing "Fit to page"
Going 'square' would seem to be the limit in one direction (after that just 
change orientation).
In the other direction I suppose you just go for 'normal' paperwidth (200mm 
or so) by a length tending towards infinity .... but the beauty of PDF was 
killing scrolling ..... for on screen texts.

> 2. A copyright notice.

Stand next to a coin-slot photocopier for a while ;-)>

> 3. For e-books purchased from my site, an innocuous looking code that
> in fact zeroes in on a particular copy and hence a particular customer.

Interesting, but I wonder if it would work without insurance (and/or a rights 
society) to chase up offenders. Such ideas are fine to start with but 
expensive (as a small company) to police.

Just my thoughts ... I don't think anyone is 'wrong' out there, just there's 
lots of ways of looking at this.

Regards,

	Michael.