Yes. A professional photographer in Europe in the early 1920s would have had access to enlargers, and enlarging photographs was already well established by then. Earlier enlargers had even used sunlight (“solar” enlargers), and electric-light enlargers had existed since the 19th century, so by the 1920s professional darkroom enlargement was entirely plausible.

Typical workflow: the film would be developed to produce a negative, then the negative would be placed in an enlarger and projected onto photographic paper at the desired size. The paper would then be exposed, developed, fixed, washed, and dried.

For a 127-film Vest Pocket Kodak negative, enlargements would have been possible, though image quality would depend on the negative size, lens quality, focus, and exposure. By the mid-1920s there were even enlargers aimed at small-format negatives, but professionals already had workable options before that. So for your novel, a pro photographer making enlarged prints from VPK negatives in 1920s Europe is historically credible.