There are lots of sites to which you can upload PDFs and then ‘edit’ them, such as PDF Pro (pdfpro.co), which lets you upload three files per month and FormSwift Free PDF editor (tinyurl.com/zvf3g3L).
CutePDF Editor (cutepdf-editor.com) is another option, but it requires Adobe Flash, which isn’t ideal. The editing facilities are very limited and not all PDFs will load, but if the document is relatively plain and all you need are basic facilities, then it’s worth trying. It is essentially a page editor. You can delete pages, rearrange their order, insert blank ones, crop and resize them. The only editing features are the ability to add your own page headers and footers, such as titles, dates, page numbers and so on.
PDF To Word (pdftoword.com) does exactly what the name says. You select a file on your PC, upload it to the site and it emails you the Word document a minute or two later. The advantage of this is that you can use Word or another word processor to edit the text and resave the document as a PDF.
FormSwift Free PDF Editor