Pakistan reportedly produces tritium at the Khushab complex, near the Khushab-1 and Khushab-2 plutonium production reactors. Between 1985 and 1987, two German firms – Nuleartechnik GmbH (Neue Technologies GmbH) and Physikalisch-Technische Beratung – provided Pakistan with a tritium purification and production facility, tritium precursor materials, and 0.8g of pure tritium.[1] Tritium can be used to boost the explosive yield of nuclear weapons.[2]

Sources:
[1] Nuclear Black Markets: Pakistan, A.Q. Khan and the Rise of Proliferation Networks (International Institute for Strategic Studies: London, 2007); Craig S. Smith, "Roots of Pakistan Atomic Scandal Traced to Europe," The New York Times, 19 February 2004.
[2] "Global Fissile Material Report 2010: Appendix A," International Panel on Fissile Materials, December 2010, www.fissilematerials.org.