Not all documents should become documentaries, and not even public television is obscure enough a platform for "Choosing Suicide," a cold and oddly tedious one-hour tape about a woman, Jo Roman, who announced plans to kill herself and carried them out. As a privately kept record of an indefensible act, the tape might be defensible, but parading it about on television makes for a pretty sickening and pointless spectacle.

At least 20 public TV stations have decided not to show the program tonight, but it can be seen on Channel 26 at 8, followed by a one-hour discussion, "Choosing Suicide: The Implications," produced for PBS by WNET in New York. Public TV is thriving on controversy this season, and one can't help wondering if "Suicide" was scheduled partly for its attention-getting value. Perhaps the infamous cable TV tape of a dog getting shot to death over and over in instant replay should be booked according to the same rationale.

The follow-up show will incorporate use of the two-way Qube cable system in Columbus, Ohio, suggesting that home viewers there will be able to vote on whether or not Jo did the Right Thing. Or on whether, if there is such a thing as "rational suicide," there might also be rational fratricide, matricide and patricide as well.

"Choosing Suicide" is one of those cases in which one may disagree with what is being said and have absolutely no temptation to defend to the death the right to say it. Artist Roman declared that her death by 30 Seconals would be a "rational suicide," but of course the phrase is a contradiction in terms, even if one discounts the innumerable moral and religious complications. t

Normal old goodbye-cruel-world suicide is irrational because it is "neurotically involved with killing" Roman tells the camera early in the program -- whereas her upper-West Side, medecade variety is "life-liberating and enriching" and "a creative act." It begins to look as though she felt this a creative act worthy of considerable applause and attention; scenes in which she presides over cocktail-party sensitivity seminars on her impending farewell, with her sloshy paintings very prominently propped up against the walls, have a more than faintly egomaniacal tone.

It all seems so very "now," so very "media conscious," so very "in touch" with feelings one doubts are truly being felt.

The chic banter is a dead giveaway. There is much talk of being "open," of "taking control" of one's life, of being "supportive." Roman's bearded husband, a psychology professor, pays her the ultimate compliment. "Jo represents someone who really takes responsibility for her own life," he says, and in dealing with this "project" -- as she had called her suicide -- her husband says, "I've learned an enormous amount about myself."

Well, good for him.

Roman leanred in March of 1978 that she had cancer, that breast cancer was spreading to her lymph nodes and that "statistics show" that women stricken with the disease in their 60s, as she was, do not have very good prospects. She claims little fear of death but great fear of pain, and the noble logic behind this alleged selflessness is a bit hard to follow. "I don't want to have a day of pain," she says."I don't want a minute of pain."

One of her paintings is called "Proud Hope."

She compares her decision to bump herself off to "an artist doing a painting and wanting to make a last stroke on his canvas" and declares later, "It's my life canvas, and I am going to end it." Some friends and relatives demur, none perhaps more effectively than the daughter-in-law who notes there is the possibility Roman will be "damned to hell" for this gambit, but others sit there in huggy-feely admiration. "It's just very special that you can do this," says one woman, overflowing with tears of awe.

Maybe this is really a documentary ab out what happens when small circles of New Yorkers start taking themselves not just too seriously but more seriously than they take any other topic in the universe. The rap sessions are almost totally bereft of moral considerations. One friend objects by saying, "It just doesn't work for me." c

It is a repugnant ordeal, and exposing it to a home audience might be justified on those grounds -- that there is something to be learned from it -- except that everything about the program suggests endorsement of what is all but called an alternate deathsytle. Going public with private concerns -- as in the PBS film earlier this season, "Joan Robinson, One Woman's Story," about a writer's last years with terminaly cancer -- can also be seen to have a purpose, but the odd part about "Suicide" is that the intimate moments never really seem intimate. They seem mannered, posed and prissy.

If it isn't cool to deplore things any more, so be it. "Choosing Suicide" is deplorable from the word go, and to the word, stop.