If you have Adobe Acrobat (the real deal, not just the reader) you can insert graphics into PDF docs, but it is not intuitive - mainly because Acrobat can only cut and paste graphics within itself, not to/from other programs.
- Click Document menu → Insert Page
- In the Browse window, change the file type to your graphics format (GIF, JPG, etc) and select your graphics file.
- The image will be inserted on its own page.
- Click the TouchUp Object tool on the toolbar. Right-click the image and select Cut.
- Go to the page where you want the document and Paste in the image. Drag & drop the image to its correct location.
- Click Document menu → Delete page and delete the (now-empty) page you just inserted.