Creating PDFs from scratch can involve a lot of effort. You'll almost certainly find the easiest solution is to use a third-party PDF component, of which there are many available on the market today.
For the .NET Framework, ABCpdf , iTextsharp and PDFSharp should do the trick. All available for free*. Each component has strengths and weaknesses, so finding the best one for a particular task requires a little research.
You'll find each component offers a unique set of basic drawing commands. These enable you to construct valid PDF documents. They may also provide additional drawing methods for laying out documents, such as System.Drawing, PostScript, HTML & CSS, etc.
The following C# code shows how simple creating a PDF document can be...
You should provide the question in more detail. If your requirement is only to save some record in pdf format there is built in methods to save a document as pdf files.