1. A portable camera device comprising: a first casing, wherein said first casing is a base; a second casing containing a lens module and having a lower part connected to a first connecting position of said first casing such that said lens module is arranged above said first casing, wherein said second casing is a camera casing containing said lens module therein, wherein an opening is formed in an upright surface of said camera casing for exposing said lens module, wherein said upright surface is disposed adjacent to said lower part of said camera casing, said lens module is an optical element containing an optical mechanism; and an extendable mechanism having a rear end with a document holding structure for holding an edge of a document and allowing the document to extend away from the holding structure at a non-parallel angle relative to the extendable mechanism, and a front end connected to a second connecting position of said base via a first pivotal mechanism, wherein said first and second connecting positions are respectively front and rear sides of said base, wherein said extendable mechanism is selectively folded or unfolded with respect to said base when said extendable mechanism is rotated in various directions by adjusting said first pivotal mechanism, and a relative spatial correlation, including focal length and angle between said lens module and said document is user-adjustable such that said lens module is focused on a selected area of said document for capturing an image of said document, wherein said lower part of said camera casing is fixed on said front side of said base, and said extendable mechanism comprises: a first extension plate having a front end pivotally coupled with said rear side of said base via a first pivotal mechanism; and a second extension plate pivotally coupled with a rear end of said first extension plate via a second pivotal mechanism, wherein said document holding structure is arranged at a rear end of said second extension plate.