ConvertProKit is a free online toolkit of file tools that run in your browser. The page claims 100+ tools, including PDF merge and compress, image conversion, OCR, unit converters, and text and developer utilities.
It is free with no account, and no usage limits are stated. The page says files are processed in the browser and not uploaded. The site's FAQ says it is separate from similarly named Convert Pro products.
Most file converter sites ask you to upload your files or sign up first. ConvertProKit was built so everyday file tasks, like merging a PDF or resizing an image, work in the browser with no signup.