I want to use PDF or equivalent, can I
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If you mean edit a PDF just like you would a Writer document: no.
PDF is only a display format. Any information concerning the logical relationship of words, phrases, paragraphs is lost when you create a PDF. Consider it is a graphical format where shapes are character glyphs positioned on the page.
All you can do is play with these shaped in the drawing application Draw.
PDF is fine to send a (nearly) unmodifiable copy of your document. As an author, when you work on your document, always use .odt format. And keep your original file as this. If you delete it and keep only the PDF, you must retype everything.
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