RICH AND BIG: Right now, a company apparently has to be both when it comes to being a leadplayer in the world trade automation movement.

Strengths and weaknesses of the world trade automation movement were displayed at the International Trade and Computerization Conference last week.The conference was sponsored by the New York-based International Trade Facilitation Council.

Among the greatest strengths:

* Users. Among those present were many leading importers and exporters. Shipper registrants ranged from Union Carbide Corp., Danbury, Conn., to Avon Products Inc., New York.

* Experience. A growing list of companies are doing business internationally with electronic messages instead of paper, although their numbers still are small. These corporations are evidently more than willing to share their knowledge with other potential users.

* Stability. It is increasingly apparent that when it comes to world trade, the U.N.-backed Electronic Data Interchange for Administration, Commerce and Transport is the leader, though there still are rumbles of discontent.

* Resources. From software suppliers to fully computerized brokers and forwarders, companies involved in world trade have a growing number of places to go for help and support; sometimes for a price, sometimes not.

* Reassurance. This one comes from the U.S. Customs Service. Customs' tone is no longer strident. The agency is still demanding a lot from the trade community, but it seems willing to acknowledge and deal with user fears.

* * * * *

SMALL AND GROWING SLOWLY: That's the population of companies that have automated their international transactions and the speed of its growth.

Mixed in with the good news at last week's gathering were plenty of rough spots:

* Attendance. Registration failed to grow from last year's numbers, at about 700. Organizers were satisfied with the figures, although some exhibitors complained. But the low total is a strong signal that international trade automation has a long way to go before it becomes a mass movement.

* Resistance. The bad news, abundantly apparent at the meet, is that many companies that make the shift to paperless trading instead of talking about it hit a wall of difficulties. Frictions that were hidden in the planning stage frequently become painfully visible once action begins.

* The law. Legal eagles still haven't quite figured out what to do about conducting business with electronic messages instead of paper documents. ''Model documents" have been published and comparisons with other technologies made; but when push came to shove, the legal experts could only say they don't know what the truths of the law are. Chances are they won't until some good, hot lawsuits are settled, either.