You can find the full movie script here, which mirrors the dialogue found in subtitles.
Modern releases of the film are almost guaranteed to include high-quality, professional English subtitles: North by Northwest subtitles English
The 65th Anniversary 4K UHD release (2024) features remastered audio and multiple subtitle tracks, including English SDH. You can find the full movie script here,
Official scripts like the one hosted by UNE Portfolio provide the full dialogue along with scene descriptions. North by Northwest subtitles English