How do I flip images in CC-illustrator?

IC,

When you reflect as described by Lutz either way (the second option is Effect>Distort & Transform>Transform, then tick Reflect X; it it is a bit more than just Object>Transform>Reflect, but I believe I should prefer that, maybe sillily)

the reflexion will be across a vertical line through the centre of the Bounding Box of the (collection of) artwork.

If you wish to completely control, or even shift, the area where the print will be on the page, you may create a and place a rectangle with no stroke and no fill, larger than the combined artwork, and select that with the artwork when you reflect; you may Group the lot (it is not necessary, but you may avoid leaving something behind; on the other hand, you will have to Direct Select artwork, unless of course you just wish to apply the Type Tool to edit Type).

Such a rectangle may be easier to align with the page.

Object --> Transform --> Reflect.... Or use the Transform effect.... or flip it in your printer driver settings.... or whatever... By all means, do read the help!

Mylenium