WingArc1st Inc. (Headquarters: Minato-ku, Tokyo; President and CEO: Jun Tanaka; hereinafter referred to as WingArc) and Cybertrust Inc. (Headquarters: Minato-ku, Tokyo; President: Yuji Kitamura; hereinafter referred to as Cybertrust) have jointly developed a digital trust service, "Trustee eSeal," to prove the issuer of PDF documents, and will begin offering it on June 30, 2026 (Tue). Against the backdrop of the widespread adoption of generative AI, the risk of tampering with electronic documents is increasing, with malicious instructions or false information that cannot be visually confirmed being embedded. For corporate business transactions, ensuring authenticity is a crucial element. In response to this situation, WingArc, in collaboration with Cybertrust, has newly developed "Trustee eSeal" to prove the issuer of PDF documents, in addition to "Trustee Timestamp" (Note 1), which proves the existence time of PDF documents. "Trustee eSeal" adopts Cybertrust's "iTrust eSeal Certificate" (Note 2) and expands the functionality to apply eSeals to "Trustee," a ledger platform. By applying "Trustee eSeal" to a PDF, it is possible to prove "which organization issued it and when." Recipients can confirm the issuing company and corporate number, thus 100% proving the issuing company and ensuring the reliability of electronic documents. Furthermore, "Trustee Timestamp" will be provided free of charge to users who contract "Trustee eSeal." By combining proof of "who issued it (Trustee eSeal)" and "when it existed (Trustee Timestamp)," the authenticity of electronic documents can be strongly guaranteed. This service is the result of a collaboration agreed upon in March 2026 to build a digital trust infrastructure for the AI era, promoting both legal reliability and operational efficiency in the complete paperless transition of inter-company transactions, and realizing a highly data-driven society suited for the AI era. (Note 3) PDFs, eSeals, and timestamps that comply with in