Thanks for your inquiry and sharing your issues here.
For us to fully reproduce the issues on our side we will need the input document for testing. Could you please attach that here for us? All attachments made on this forum by you are completely private and can only be downloaded by you and Aspose staff.
Additionally you can choose to e-mail me your files directly by clicking the “Contact” button above this post and choosing the E-mail option.
Given your descriptions I can make a few comments now:
a) This is probably caused by a text frame, if this it converted to textbox the issue may not occur.
d) The difference in file size maybe due to fonts being embedded in the output PDF. Currently Aspose.Words embeds all fonts into the document, even “standard” fonts such as Arial whereas applications such as Microsoft Word do not.
e) There are no limitations to file size in Aspose.Words, the only restriction is the amount of RAM on your machine. However, please note Aspose.Words converts documents to PDF only, it does not work with existing PDF documents. If you are looking to concat PDFs you will need to use Aspose.Pdf to do this.