Getting the first page of a fixed document sequence as a reference page to know how to set page orientation. Assumes that all pages in the document are the same size and same orientation as page 1.

gistfile1.txt

        /// <summary>
        /// Gets the PageOrientation of the first page of a fixed document sequence, based on that page's dimensions.
        /// </summary>
        /// <param name="docSeq">The fixed document sequence.</param>
        /// <returns>
        /// If the first page could not be found, returns Unknown.
        /// Returns Portrait when the page width is less than the height.  
        /// Otherwise (width is greater than OR EQUAL), returns Landscape.
        /// </returns>
        private static PageOrientation GetPageOrientationOfFirstPageOfFixedDocSeq(FixedDocumentSequence docSeq) {
            PageOrientation orientation = PageOrientation.Unknown;

            FixedPage firstPage = GetFirstPageOfFixedDocSeq(docSeq);

            if (firstPage != null) {
                orientation = (firstPage.Width >= firstPage.Height) ? PageOrientation.Landscape : PageOrientation.Portrait;
            }

            return orientation;
        }

        /// <summary>
        /// Gets the first fixed document in a fixed document sequence, or null.
        /// </summary>
        /// <param name="docSeq">The fixed document sequence</param>
        /// <returns>The first fixed document, or null.</returns>
        private static FixedDocument GetFirstDocumentOfFixedDocSeq(FixedDocumentSequence docSeq)
        {
            FixedDocument firstDoc = null;

            if (docSeq != null && docSeq.References != null && docSeq.References.Count > 0)
            {
                DocumentReference firstDocRef = docSeq.References[0];
                firstDoc = firstDocRef.GetDocument(true);
            }

            return firstDoc;
        }