Painter, printmaker, and photographer Paul-Adolphe Rajon was born in Dijon, France, in 1843, the youngest of three children born to Jean-Maris Rajon and Caroline Jaugey. His artistic career began as an apprentice to photographer and brother-in-law Pierre-Joseph Meurisse in 1857, focusing on retouching portraits. He then enrolled in a painting course at the Metz School of Design under Auguste Migette from 1859 to 1860.

Following completion of this course he moved to Paris and found work as a professional retoucher, continuing his painting studies at the Ecole des Beaux-Arts under Isidore-Alexandre-Augustin Pils. He also studied printmaking under Léon Gaucherel and Léopold Flameng, focusing primarily on etching portraits. The success found with these portraits led to commissions from L'Art, Gazette des beaux-arts, and, later, PG Hamerton's The Portfolio. His work was frequently published by Goupil Galleries.

Along with friends and fellow artists Emile Boilvin, Felix Braquemond, Louis-Charles-Auguste Steinheil, and Philippe Burty, he entered his artwork into the Paris Salons, debuting in 1865. He won medals in 1869, '70, and '73, as well as at the Exposition Universalle of 1878. In the midst of working and exhibiting, the Franco-German War of 1870 took place and Rajon enlisted in the National Guard Battalion, seeing action at La Malmaison. He returned to Paris following the war and once more began exhibiting, to critical success throughout France, Great Britain, and the United States. Beginning in 1872 divided his time between Paris and London, exhibiting at the Royal Academy, the Royal Institute of Painters, Walker Art Gallery, and Manchester City Art Gallery. In the latter, he kept up a professional connection with New York-based print dealer Frederick Keppel.

Rajon was especially known for his etched portraits of noted writers, artists, scientists, and others, among them Charles Darwin, George Eliot, James McNeill Whistler, and many others. His work can be found in the National Portrait Gallery, London; the Metropolitan Museum of Art, New York; the Art Institute of Chicago; and the Smithsonian American Art Museum, among others. 

Paul-Adolphe Rajon died of pneumonia on June 8, 1888, at Auvers-sur-Oise.