Sure you can open V4 drawing (.model) to CV5, print, view etc. to it. Then you can copy any data from it (just selects from drawing tree + Copy) and create new CATDrawing (V5 drawing) and there Paste => drawing migrated to V5. Dataloss is quite minimal, performance can be bad, but mainly it actually works.
For larger amounts of data, you can use Utility that doesbatch conversion of drawings.
But if you want to save V5 drawing to V4... then you are in trouble.
If you do not wish to preserve links because the V4 to V5 data structure ends up being so dissimilar (in cases of model files with a large number of filtered solids) then you can copy + paste special AS RESULT and you will get V5 views with just normal, unassociated draw data.
You will however occasionally see formatting changes in Text and some dimensions. Leaders may look different due to the different creation styles. Also, in V4 they used "symbol libraries" a lot which is similar to V5 catalogs to place 2D components. When migrated some of these may have their show/noshow status changed.
To be absolutly sure you have no physical changes between the actual printed V4 drawing and a V5 drawing you would have to take an HPGL file (a printer language output file) and open it in some third party program, save it as a DXF file then open that in V5 CATIA.....the result will be a V5 drawing with no links but 100% accuratly reflects the contents of the V4 drawing thus eliminating any cleanup of translation errors which occur but also results in a file with little or no value other than archiving legacy data.