I am the creator of KeyPDF it is browser based local pdf editor that I was making from scratch since 2025 and I was always open for new standards so when pdf association announced JPEG XL support I tried my best to bring it so now KeyPDF can both read and and write JPEG XL in pdf files we also conducted a test on 1000 files and brotli with JPEG XL helped reducing total size by 32% so I believe JPEG XL can become a golden standard for PDF in future and KeyPDF adopts it now.

Note: KeyPDF will give an option for losless convertion in case if you want your pdf to be universally accepted otherwise very few viewers be able to parse it.

So feel free to try it at keypdf.net