Publishers have particular rules about which formats of journal articles are allowed to be published in research repositories. There are some that will allow you to publish the published version, but many ask that you upload the accepted manuscript, after it has been peer reviewed, but before it has been formatted for publication. Some are more restrictive and might only let you upload a preprint.
You can find out this information by searching for the journal title in SHERPA RoMEO to find what the publisher's policy is.
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