If you want to change the options of the PDFObject (the embedded PDF viewer), you can use global or page level Client Script (see Server Events and Client Scripts in the help file), e.g.
ew.PDFObjectOptions = {
width: "600px",
height: "600px",
pdfOpenParams: {
toolbar: 1
}
};
The PDFObject viewer will use the specified sizes and have a toolbar which allow user to have more controls on the PDF.
See PDFObject API for complete information about the available options.