NIH has updated their recommended font list for applications submitted on or after Jan. 15, 2017. Following is a summary of guidelines that will apply to text in PDF grant application attachments:

• Text color: Perhaps the most notable change, text in PDF attachments is no longer restricted to the color black. Though not required, black or other high-contract colors are recommended. Read: no fuchsia comic sans.  
• Font size: Must be 11 points or larger. Smaller text in figures, graphs, diagrams, and charts is still acceptable as long as it’s legible when the page is viewed at 100%.
• Type density: Must be no more than 15 characters per linear inch (including characters and spaces).
• Line spacing: Must be no more than six lines per vertical inch.
• Recommended fonts:  Arial, Georgia, Helvetica, Palatino Linotype. Other fonts are acceptable if they meet the above requirements. See the Font FAQs for additional guidance.

Still have questions? Learn more about formatting attachments here.