Paul Heigl studied history and geography in Graz and Munich and was awarded his doctorate in 1910 from the University of Graz. From 1909 to 1911 he also trained at the Institut für Österreichische Geschichtsforschung (Institute of Austrian Historical Research) in Vienna as an archivist and historical research assistant, becoming a librarian in 1912. Since his student days he had been a member of völkisch fraternities, such as the Studentenfreikorps-Wien in the Heimatschutz. No further details of his activities are available, but he himself stated in June 1938 in a personnel questionnaire attached to the Gau file that he had been active "from 1932 in the intelligence service for the Gau of Vienna and than in the Austrian NSDAP office in Munich". He joined the NSDAP and SS in 1933 and was arrested on 12 August 1934 for his part in the National Socialist July putsch, which resulted in his dismissal as a librarian. After the German Reich Ministry of Education, with the aid of its Austrian counterpart, obtained authorization for him to leave for the German Reich, Heigl worked as a librarian in Greifswald and Berlin. In the view of the Nazis, he was therefore seen as an ideal candidate after the annexation of Austria to the German Reich for the post of director of the National Library in Vienna. He took up this position in March 1938 and, in contrast to other Nazi appointments at this time, was notable for his expertise and management skill. Heigl himself was disappointed at the personnel situation in the National Library, where only one staff member had been a member of the (illegal) NSDAP, as he pointed out in one of his first meetings with the Reich Ministry of Education directly after his appointment in March 1938. The staff changes at the National Library began with Heigl's direct involvement on 16 March 1938 with the arrest of director Josef Bick. In subsequent months a number of librarians were dismissed or forced to retire. Four staff members were retired for "racial" reasons and eight retired or dismissed with immediate effect on political grounds. Thus, twelve of the eighty-nine staff members were victims of this "cleansing". In order to participate in the expropriation of books belonging to persecuted individuals or institutions, Heigl made more active use of his connections to the Nazi administration, the Gestapo and the Security Service (SD) than other library directors at the time. He was able in this way to considerably enlarge the National Library's holdings, acquiring around 500,000 expropriated items between 1938 and 1945. He was supported in this by his collection heads, who were well informed of the collectors and their assets. Not all of the expropriated books were signed over to the National Library. Heigl generously allocated duplicates above all to other libraries and from 1941 supported the development of the "Führer library" in the planned Kunstmuseum (Art Museum) in Linz. At the same time, he endeavoured to keep the contents of liquidated libraries in Austria and prevent their transport to the "Altreich". He also frequently and openly criticized the pulping of books by the Vienna Gestapo and SD head office. In January 1944, Friedrich Rainer, the Gauleiter of Carinthia, commissioned Heigl to distribute books, above all from seized Jewish removal goods stored in Trieste. Thereupon, thousands of books were collected in the synagogue in Trieste and transported from there initially to Carinthia. Heigl was still involved in this commission in March 1945. A month later, he and his wife committed suicide. It has not been possible to determine whether Heigl acquired expropriated items for himself.
After the war in 1945, the National Library in Vienna was found to have many other illegally acquired items apart from the books from Trieste. After the restitution to twelve collectors, including Viktor Ephrussi, Moritz Kuffner and Heinrich Schnitzler, in the late 1940s, however, thousands of volumes expropriated by the Nazis remained in the library. The National Library began systematic provenance research in 2003 and since then 46,866 objects acquired under Heigl have been restituted to their rightful owners or legal successors.