DecoTech v6.xx now remembers the last configuration you set for each kind of printout.  So you must configure the floor plan printout separately from the 3D perspective printout.

To do so, click the Print Setup button located at the right of the Print button in the Print the floor plan or in the Print the 3D perspective window.

The previous DecoTech version 5.xx was always using the Portrait orientation but the printed image was also always rotated automatically.  DecoTech version 6.xx now offers you the choice.  To obtain the same printout result as DecoTech version 5.xx did, set the paper orientation to Landscape.

See also topic #13 for a similar trouble.