Make sure that you have selected the appropriate paper source, paper size, and orientation in your printing software. (On a Mac OS-based computer, click the Page Image icon in the Page Setup dialog box; if you want to narrow the margins to print on more of the page, you can select Larger Print Area in the Options portion of the Page Setup dialog box.)
Check the paper width guide in the cassette. If the width guide is set too wide, the paper may be fed into the printer at an angle.
Also check that the margins set in your document are correct, that you are not using a type of paper that is causing a feeding problem, and that the paper cassette isn't too full.