The numbering scheme which suits the architecture of your Application suite needs to be thought through carefully.
Its highly recommended that the File Version specified in the Compile Options dialog is the same as the Package version. It is then easy to associate which installer file installed which DLL in the installed environment.
Each Application should use a different File Version number (the File Version embedded in the DLL ) so that detecting which Application installed what object is easier to work out. The first 2 digits might be the same for each Application, with the third number differing. For example, 1.1.0, 1.1.1, 1.1.2, 1.1.3 and 1.1.4 for the 5 MSI in the example below. This is for the scenario where a single publisher is producing the install. When customisations and Add-Ons are being provided by external entities, it might be advisable for the external entities to be provided with the Version number scheme to use so that no clashes occur with other installation providers. They will need at least 1 number that they may change for their various releases. Like 1.10.x, 1.11.x, 1.12.x for three external providers. And these would be releases that would work with 1.1.x of the core product.