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A folio can include articles that are landscape only, portrait only or dual. You cannot mix and match orientations within folio; the entire folio must be dual, portrait, or landscape. In your source documents, you can include horizontal and vertical layouts in the same InDesign document for dual-orientation folios, or you can create separate InDesign documents.
A dual-orientation article has two layouts—vertical or horizontal. When the user rotates the mobile device, the second orientation is displayed. A single-orientation folio is locked into that orientation. For example, if you create articles with only vertical InDesign files, that orientation remains in place even if the user rotates the mobile device. However, if a folio is portrait-only, full-screen videos can still be played in landscape mode.