The PDF format is generally used to provide electronic forms and other documents, and often these will require you to complete them out and submit them for processing some-where. Often, such PDFs are given form properties where you can click various options to edit them and give the necessary information; however, often this is not the case, and those giving away the form simply have it as a basic and uneditable PDF.
In these cases, you may have to print the PDF, fill it out by hand, and then scan it back into your system to submit; however, this is not necessary to do. A number of programs including Apple’s default PDF handler “Preview,” give the ability to mark up a PDF document, and you can simply use this as the method to fill out an otherwise static PDF form.
Clicking the text box button in the Edit toolbar will let you create a text box for data entry. You can then click the “A” button to make the font window change the text size and even font face.
With the PDF open in Preview, just enable the edit toolbar by pressing Shift-Command-A, or by just clicking the Edit Toolbar button in the standard Preview toolbar. Now you can click the text tool,and afterwards, click or click-and-drag on the PDF document if you need to create a new text box. You can then add the desired text and set the font size, color, & font face, and then resize the box accordingly to position it in the form as you want.
Repeat these steps for all areas where you want to fill the form, and then you can even sign the form using Apple’s Signature option to capture your signature and apply it to any PDF.