A PDF is a file format developed by Adobe that can contain images, text or both. PDF files can include blank form fields that a user can fill out on his computer. If you have a PDF file that includes blank form fields, but the text you attempt to enter into the form field is too large or small, you can adjust the font size of the input text using Adobe Acrobat.
Launch Adobe Acrobat on your computer. Click "File" and select "Open." Navigate to the location of the PDF file in which you want to change the font size of the form field.
Click "Tools" in the file menu and hover over "Advanced Editing." A drop-down menu appears. Scroll over and click on "Touchup Text Tool."
Right-click on the PDF form field that you wish to change the font size for and select "Properties." A Properties window appears.
Click on the "Text" tab at the top of the window, and click the up or down arrow next to "Font Size" to adjust the size of the font.
Click "Close" to save your changes.