Do I need to reveal card added with the Archived Memories?
Short answer: yes you must show the card and they will see what it is.

Visible cards remain faceup when they go to the Archive.

The Corporation must show cards chosen by effects to the Runner without changing the face-up/down status, and if it is faceup the Runner will be able to see what it is.

Only facedown cards remain hidden from the Runner unless a game effect instructs you to reveal one.

If you were to have facedown cards in the Archive your opponent would see that you picked a facedown card but not see the front of it.

From the official rules


  Revealing Cards
  
  If a Corporation card is not visible to the Runner when it is trashed
  or discarded, then it is sent to Archives facedown. If a Corporation
  card is visible to the Runner when it is trashed or discarded, it is
  sent to Archives faceup.
  
  If a specific card or card type in an inactive state is chosen by a
  card effect, the Corporation must show that card to the Runner without
  changing its faceup or facedown status. The Corporation only reveals
  the card if it was facedown and the effect says he must reveal it.