My experience of reading pdf'd text does not endear me to it - on all size
monitors up to 1028x800 (and especially on the smaller 600x480) it is
generally very tiring on the eyes unless one magnifies the page and then
you are continually moving the sidebar cursors around to view page.
Admittedly pdf page images look the same on all platforms and this may be a
big advantage (eg to maintain house style), but if all you want to do is to
present the text and not worry about page layout this advantage has a heavy
price.
For some forms of page the pdf formated page is smaller than the html -
large tables seem to benefit this way, for others the zip compression is
counterbalanced by the positioning overheads etc so page lengths tend to be
comparable or somewhat longer.  There are some security features built into
pdf but I'm not sure I would rely on them (eg simple browsers can be
prevented from saving/printing the text but these are easily overcome if
you have any of the generator tools) but as I have not really used these I
would defer to others who have more experience.
Non recognised OCR'd text is handled as gifs within stream - the early
adobe OCR was not the best available (I gave up on mine for that reason)
tho more recent versions should be better  - these gifs can look out of
place on page though obviously for either completely recognised text, or
for electronic text put into pdf this is no problem and does indeed get
over one problem of HTML when non-supported characters are encountered.
Also of course the non-OCR'd bits dont make it into any index.
My feeling is that pdf pages are very good if created in this format for
viewing on screen and not just on the printed page (pdf now seems to have a
specialised niche market in high quality direct to print-shop page
transfers as well as its much older to laser printer use) - for OCR'd
printed page images the results are generally much less pleasant to use.
Of course you are mostly still dependent on a single company for editing
tools tho now alternative pdf generators are available.

Also web search engines generally dont index pdf pages and you require
readers to have the necessary plugin (tho most will have these)

Frances Coakley Snr Lecturer Dept Elec Eng; University of Surrey; Guildford
GU2 5XH UK;
Tel +44(0)1483 259129; Fax +44(0)1483 534139 email [log in to unmask]




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