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In your Order model, you have defined a ForeignKey relationship for several other models (Annual, Issue, and Article), but each of these relationships points to the Catalog model. When you attempt to save the Order instance created by your form, it has received objects of these types (Annual, Issue, and Article), but it cannot store a foreign-key reference to these objects in the fields defined on the Order model. This is due to the foreign-key fields on the Order demanding that they can only contain a reference to Catalog objects.
If, for each of these foreign-key relationships, you wish to store one of these various kinds of objects, you will need to alter your Order model definition to expect references to objects of those models rather than Catalog objects.
In brief, I would suggest that the Order model be modified to include the following relationships. This will allow an order object to store a single reference to an object of each other kind (Annual, Issue, and Article).
annuals = models.ForeignKey(Annual, related_name='annuals_ordered', blank=True, null=True)
issues = models.ForeignKey(Issue, related_name='issues_ordered', blank=True, null=True)
articles = models.ForeignKey(Article, related_name='items_ordered', blank=True, null=True)
For more information about ForeignKey relationships in Django, see the reference here.