If you go to:-
Catalog / View / Business Settings / Options and tick the Enable Extended
Product Description for Customer Reports this gives you an additional text
field that won't appear on any of the product or cart pages but does appear
on the printed receipts that you create with Actinic Order processing. Use
this for your secret passkey. The user then gets this when the invoice is
mailed to him.

Now that's maybe too slow for most customers (or you don't intend to post
anything) so for a a more instant solution read on:-

It would be very easy to modify OrderScript.pl to lookup the REPORT_DESC
data (that's what the Extended Product Description text mentioned above is
keyed on in the .cat files)
and to include it on the customer e-mail and / or the final order
confirmation page (the one with the DONE button) as these are only sent /
displayed after payment is made.

If you're using off-line credit card processing or expecting significant
fraud you may not want to go this route as a fraudulent customer can get a
passkey with little effort (CC # 0000 0000 0000 0000 anyone?).

Detailed patching instructions (for Customer E-mail only).

Backup OrderScript.pl (your Site1 version).    Now open OrderScript.pl in a
text editor (not a word processor).

Search for the line "sub GenerateCustomerMail".    Assuming you find that
then you're now at the start of the required routine.   
Now search for "# Add component descriptions" and you'll find a block 
of code like below:-

********************************

		$ACTINIC::B2B->AppendXML('CART', "\r\n");
		my $nLine;
		for( $nLine=0; $nLine<$nCurrentRow; $nLine++ )				# Store the whole table
			{
			for( $nCol=0; $nCol<$nColumn; $nCol++ )
				{
				$ACTINIC::B2B->AppendXML('CART', sprintf($TableFormat[$nCol],$pPrintTable->[$nCol]->[$nLine]));
				}
			$ACTINIC::B2B->AppendXML('CART', "\r\n");					# Terminate the line
			}

		#
		# Add component descriptions
		#
		$nCurrentRow = 0;  									# Start at the top
		my $nComponentCount;
		$pPrintTable = [];									# Start again here
		for ($nComponentCount=0; $nComponentCount<=$#ComponentLines; $nComponentCount++ )


********************************

Immediately above the

		#
		# Add component descriptions
		#

stick this bit of code


		# add in Extended Product Description				      # start of patch
		if ( $$pProduct{"REPORT_DESC"} )				      # (V11) if we have extended description text
                        {
			$ACTINIC::B2B->AppendXML('CART', "\r\n");  		      # space down
			$ACTINIC::B2B->AppendXML('CART', $$pProduct{"REPORT_DESC"});  # add the Extended Description text
			$ACTINIC::B2B->AppendXML('CART', "\r\n\r\n");  		      # terminate line
                        }       						      # end of patch


Update your site and test to destruction.   Remember that Actinic don't
support patched scripts.   Also note that this text goes into the customers
confirmation e-mail and shouldn't contain html tags but as long as you pass
the text of a fully formed url in Extended Product Description e.g. 
"To download your file please go to http://myserver.com/download/filename.zip and save to your disk"
then that should be clickable in
most modern e-mail clients.

Regards . . . Norman