When sourcing cotton linen paper, you must prioritize GSM (Grams per Square Meter), typically ranging from 80gsm to 300gsm depending on the use case. Ensure the fiber ratio (e.g., 75% cotton and 25% linen) is clearly defined, as this affects the texture, durability, and ink absorption. For archival purposes, verify that the paper is acid-free and pH-neutral to prevent yellowing over time. Additionally, check for watermark customization capabilities if the paper is intended for security or high-end branding.