This is readable and has line numbers. The pages are a little thin, but they do hold up to writing and highlighting: Link
I didn't click on this link immediately so i didn't realize it was to a printed version.
I guess in addition to that we need a link to something public domain at Archive.org in PDF - presumably a Jowett translation (?) - that has line numbers and potentially annotations. An older Loeb edition?
A quick search of Archive.org has not been productive. It looks to me that for best word-searching ability we need a single PDF containing all of Jowett's edition of Plato's dialogues, which was apparently in seven volumes, with the last version being a third edition. It's well over a hundred years old so should be freely available.
Strangely there does not seem to be a free older Loeb edition -- possibly because the Jowett pre-dated that and was considered the gold standard (?)
I also see a Thomas Taylor edition but I don't know the reputation of that.
Further notes:
Archive.org seems to be damaged from its problems last year. The older Jowett editions which ought to be public domain are not downloadable easily, which chatgpt points to this edition which is much newer.
I will check Hathitrust - not productive.
It appears that the Online Libreary of Liberty has the full Jowett Series.
This appears to be a master link from which the full set can be assembled.