Put this in the theme file somewhere near where you output the_content() (likely in the single.php or page.php file) to make a link you can click that takes you into the admin to edit it. This link will only be visible when the viewer is logged in and has appropriate permissions to edit that page (administrator or author).
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Ovidiu Purdea, WordPress Webmaster and SEO & SEM specialist with over 9 years experience in this field. Guru using, modifying, adapting websites based on WordPress. You can follow Ovidiu Purdea on my Google+ profile.