Here are the official definitions:
PMG uses the designation Exceptional Paper Quality (EPQ) for notes that, in the opinion of PMG graders, are original. By original, we mean that a note has not been physically, chemically, or materially processed to lend the appearance of a higher grade. PMG graders examine the embossing, inks, and overall integrity of each note to make the determination whether it will qualify for EPQ. Notes exhibiting normal wear-and-tear for their respective grades are eligible; normal wear may include factors affecting grade such as counting marks and folds. Notes receiving the EPQ designation must furthermore be unrestored. A restored note has had non-original material added to bring its appearance to a known or assumed state.
PCGS will affix a “PPQ” (Premium Paper Quality) designation to the grade (e.g.: “Gem New 65PPQ”). These are notes that bear no visible evidence of restoration and that retain all signs of fully original paper quality, such as paper wave, embossing, and bold ink color and eye appeal. “PPQ” notes should also have above average paper for the grade that is free of defects such as tears, pinholes, or other problems. This is not done to penalize those notes that are not fully original, as many are very collectible and highly valuable. Instead, this system is designed to reward those notes, both circulated and New, that possess premium paper quality and complete originality. It should be understood that even though a note may be fully original and free of any restoration, it still might not qualify for the “PPQ” designation.
BCS states: If a note is unaltered and has not gone through a restoring process and receives the grade of EF or higher it will receive an auxiliary designation of ORIGINAL stated on the holder directly beneath the number grade.