PDF Editor

PDF is generally the final printed stage of something you work on. The worst option is to edit the PDF once it is completed. The best option is to edit the original file in what you created it in and then re-PDF it. LibreOffice can create PDFs from any file it works with (documents, spreadsheets and presentations) and works very well.

Think of PDFs as the final output. The MP3 or JPG final from the original source sound file (in WAV or similar) or image file (in PSD, XCF, etc). It's always best to work from the original and not mess with a PDF as each time its edited it gets messier and messier internally.

Foxit can create and edit its own PDFs natively but can not edit an existing PDF from elsewhere unless you buy the full version.

LibreOffice Draw can also be used to edit many PDF files.

Although it silently converts them to .odg format during the editing process, you can export them to PDF again as John stated above.