Depending on the current display mode, the keyboard & mouse interface differs slightly.

Multi-Page Mode

When two or more pages are displayed at the same time, the following keys are available:

Home - Positions to the first group of pages, starting at the first page.  The first page becomes the current page.
End - Positions to the last group of pages, ending at the last page.  The first page of the displayed pages becomes the current page.
Control+Home - Same as the Home key.  Positions to the first group of pages, starting at the first page.  The first page becomes the current page.
Control+End - Same as the End key.  Positions to the last group of pages, ending at the last page.  The first page of the displayed pages becomes the current page.
Left Arrow - Moves to the previous page.  The displayed group of pages is adjusted if necessary.
Right Arrow - Advances to the next page.  The displayed group of pages is adjusted if necessary.
Up Arrow - Moves the first page of the displayed group of pages to the previous page (or sheet in duplex mode).  The current page is adjusted if necessary.
Down Arrow - Advances the first page of the displayed group of pages to the next page (or sheet in duplex mode).  The current page is adjusted if necessary.
PgUp - Displays the previous group of pages.  The current page is adjusted if necessary.
PgDn - Displays the next group of pages.  The current page is adjusted if necessary.
+ (numeric keypad) - Zooms in.
Escape - Generates a NM_SFTPRINTPREVIEW_CLOSE_CODE notification.
Return - Generates a NM_SFTPRINTPREVIEW_RETURN_CODE notification.

Clicking on a displayed page with the left mouse button will switch to single page mode (zoom in).

Single Page Mode

Home - Positions to the top of the current page.
End - Positions to the end of the current page.
Control+Home - Positions to the top of the first page.
Control+End - Positions to the end of the last page.
Left Arrow - Horizontally scrolls left on the current page.
Right Arrow - Horizontally scrolls right on the current page.
Up Arrow - Vertically scrolls up on the current page.
Down Arrow - Vertically scrolls down on the current page.
PgUp - Vertically scrolls up on the current page.  At the top of the current page, move to the bottom of the previous page.
PgDn - Vertically scrolls down on the current page.  At the end of the current page, advance to the top of the next page.
+ (numeric keypad) - Zooms in.
- (numeric keypad) - Zooms out.
Escape - Generates a NM_SFTPRINTPREVIEW_CLOSE_CODE notification.
Return - Generates a NM_SFTPRINTPREVIEW_RETURN_CODE notification.

Clicking on the displayed page with the left or right mouse buttons will zoom in/out, depending on the settings defined using SetControlInfo, SFTPRINTPREVIEW_CONTROL, iZoomStyle member). 

When pressing the left mouse button, the page may be repositioned (dragged), depending on the settings defined using SetControlInfo, SFTPRINTPREVIEW_CONTROL, fDragPage member).