How to Set Resolution for Illustrator & Save As PDF
Illustrator is a graphic editing software produced by Adobe. Illustrator works with the vector graphic format. Such a format contains a mathematical description of an image rather than a collection of pixels as any traditional graphics. Advantages of the vector format include the small file size and scalability to any resolution without losing the graphic quality. When exporting a vector image to another format such as PDF (Portable Document Format), Illustrator allows you to explicitly set a desired resolution for your document.
Click the "File" menu in Illustrator and choose the option "Document Setup."
Select "Printing & Export" using the drop down box in the window "Document Setup."
Enter the desired resolution in dpi (dots per inch) - 600, for example - in the box "Output Resolution." Then click "OK."
Click the "File" menu again and select "Save As."
Select the option "Adobe PDF" in the box "Save as Type."
Type a desired name in the field "File name" and click the button "Save."