By default all specific printer name settings are stored inside file “*\Clients\webserver\printer.bin

Here example
PRINTERS=PS:%DEFAULT%%PRINTMENU%MS Publisher Imagesetter%Universal Printer %;PS:%PRINTHIDE%MS Publisher Imagesetter%Hidden Menu Virtual Printer %;

1. PS: = says it is PostScript format of driver
    possible are PS:  PostScript
XPS: XML Paper Specification – Microsoft’s format
PCL6: Printer Command Language
PDF: Adobe’s format
    which but require supporting format converter and printer driver.
    In example %MS Publisher Imagesetter% is PostScript driver.

2. %DEFAULT%%PRINTMENU% = tells it should be default chosen printer and printmenu tells 
    to display generated pdf content.
                        Possible are following values
%DEFAULT% => allowed to be set only once by one printer, do not set it twice or more!
                           This setting makes printer default. 
                           Remove this tag by all simulated printers to use systems default preferences.

%PRINTMENU% => display pdf window, should not be mixed with printhide since excluding 
                           each other in parsing sequence!

%PRINTHIDE% => hide pdf window, requires browser with pdf mark support 
                           else print popup will never fire, as example Safari Mac does not support it.

%PRINTMARK% => by default activated on printmenu/printhide
                           It is auto printpopup mark of PDF language.

%NOCONVERT% => provides printer data without converting to PDF format.

%FORCEUNKNOWN% => skips print file format check, for mixing with noconvert.

%EXTRA_OPTS([extras])% => extra options passed to converter attached on start
                           EXTRA_OPTS + OPT_PS
                           Example: %EXTRA_OPTS([%nopdfmarks%])% would forcibly 
                           disable print mark passing to PDF converter. 

%JOINDELAY(1000ms)% => concatenates prints to one file if new print arrived 
                        in lesser than given time in milliseconds. 
PS:%PRINTMENU%%JOINDELAY(4000ms)%MS Publisher Imagesetter%Next Universal Printer %;
                        That example will postpone print converting for at least 4 seconds.

3. %MS Publisher Imagesetter% = tells to use default Microsoft printer driver, you may choose here any printer driver present on server but be aware that such printer driver is compatible with converting program, “MS Publisher Imagesetter” is PostScript format driver. Microsoft does not accept all drivers to be used for printing conversion.

4. %Universal Printer %; = tells how the printer should be named when displayed inside RDP session in available printer menu. Notice, all wished printers are separated by semicolon “;” as in example on top. 

PS: remember, the name of printer displayed in session gets automatically attached in string (redirected *xyz*) and can not be controlled from client side.

UPDATE: on latest RDPlus updates to get highest compatibility with all browsers that do not have support of PDF auto print popup mark the default setting in “*\Clients\webserver\printer.bin” is to display PDF frame anyway with %PRINTMENU%, to change it just replace that setting by %PRINTHIDE% and restart HTML5 server in AdminTool GUI!