Blueprint Flipper is able to flip blueprints horizontally and vertically, has two buttons on the top of screen and hotkeys.

With a blueprint or blueprint book in hand, click on the associated button to flip the blueprint. Alternatively you can use the hotkeys:

Shift+z for Horizontal
Shift+x for Vertical

This version is updated for the 0.16 version of Factorio. Its just my reupload with small fix (GUI etc...) So use it at your own risk and feel free to remake it into fully working mod.

Known issues: curved rails.

Credits to original authors: humpfry, GopherAtl, Roktaal