Converting PDF content into HTML is not a trivial task, and we understand that you may feel frustrated when converting documents (especially PDFs) to posts. When we migrate sites for clients, we have dedicated people who spend their time recreating the content in HTML. It's a big job, and ultimately worth it.
In general, it is best to paste from the source document (e.g. a Word document and not a PDF.) Some of the trickiest parts include dealing with bullets and tables. With bullets, we usually remove the bullets added by the program using a find and replace function and then add bullets again using the HTML editor. (Which we sometimes call the WYSIWYG, its technical industry name.) Tables must be recreated altogether. (Unless you find some clever way, in which case, please share!)
If you're not able to utilize the original Word documents, pasting from a PDF get tricky because PDFs are designed to be difficult to edit and inherently aren't easy to copy and paste into other programs. Linebreak issues are especially prevalent with PDFs, and require using notepad to find and reset the breaks. It's a difficult process. If the publisher or the PDF can enable a setting called "accessible PDFs" it will include linebreak information making it easier to copy and paste out the text without linebreak problems.
Also, for really complex PDFs (with large charts or illustrations) we sometimes just add a summary for the post and then attach PDF and call it a day. It depends on how we think users are going to utilize the content. While it's generally better to have the content in the post, sometimes it just isn't feasible to do so.
If you cannot find the source documents and you must copy and paste from PDF, we do recommend Notepad (not to be confused with Wordpad) which is a plain-text editor for the PC, or using TextEdit for a Mac. While you can't add any formatting or do anything special, it may help me get content in and out and may help you see and quickly correct any linebreak issues, especially when the "word wrap" option is turned off.
If you find yourself overwhelmed or you need assistance, please don't hesitate to contact us! We do have migration services for those who need to move a large amount of complex content.