Shalabh - thanks for your question. I am going to move it to the community specifically for that product. This area is for general community questions and suggestions.
Depending on which product/flow you are using, PADS Netlist, PADS Integrated project, PADS Professional or Xpedition the answer varies to some degree. Basically it is necessary to have a unique part number per part for packaging, but you can achieve this in a couple of ways.
From your use case the simplest answer is that you will need to identify each variation of a 1206 resistor in your Databook database, so for each value you will add a new record, most of the fields will be identical, but Value (and maybe part number) will be different. This allows you to place the symbol and annotate the necessary information to get the part you actually want to use and more importantly fit on the board.
Assuming you have the right entries in Databook you may still copy the resistor in the way you state and change its value, Live Verification will then find an incomplete match, probably first time it will say no matches - you then select the offending symbol in the schematic and do a 'Load into Databook'. This will show matched and unmatched properties - remove the conditions you are not interested in and Databook will then search for a 1206 resistor with th correct value - once identified you annotate the correct properties to the selected component.