As above, recommend Acrobat X Pro for the additional accessibility features.
For basic accessibility, if you're including tables then tick the 'repeat as header row' box regardless of whether it goes over the page or not. This flags the top row to convert as TH cells and not TD cells.
If you're using images and working in DOCX format, save it as a DOC format before you save it as a PDF. Otherwise your images will be bunched up at the front in the tags list and won't read out in the right order to a screen reader even if you define the reading order with the Tough Up Reading Order tool.
If accessibility is a focus or if you have policy or legislative obligations around accessibility then the most appropriate resource will be the sufficient techniques for PDF published on the W3C's Web Content Accessibility Guidelines website.
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