If you are posting to a thread, look at the little icons right above where you are typing. The fourth from the right, looks like a little window with a thin black line around it and black dots at the corners. Click on that and then follow the directions. It allows you to go to your computer and attach pics or files, including pdf. They will appear wherever your cursor is, so if you want them below your written word, move your cursor down there before you start the process.