Created Unassigned: output pdf file have only one page [1213]

Hi, all!

first sorry my English.

Magick.NET is great!
but I have a little issue.
this is not an issue with Magick.NET, but i can't ask it in usual programers forum, because it directly relates to Magick.NET and I hope to get help here.
here is a problem:
there is 300 jpg files. size is about 500 Kb each. I need to create one pdf from these 300 jpg. I used an example from documentation - Create a PDF from two images - and it works fine! but if there 300 images, program starts to eat 1,5 Gb of memory. this is not acceptable for me. I find another way to do this and here is my code:

```
using (MagickImageCollection collection = new MagickImageCollection())
{
string[] jpgs = Directory.GetFiles(@"c:\PDF\", @"*.jpg");

using (FileStream fs = new FileStream(@"c:\PDF\out.pdf", FileMode.Append))
{
foreach (string jpg in jpgs)
{
MagickImage img = new MagickImage(jpg);
img.Format = MagickFormat.Pdf;
collection.Add(img);
collection.Write(fs);
fs.Flush();
collection.Clear();//if don't do this, memory will grow very fast
}
}
}
```

Output pdf file have a size by which it can be argued that there is all of images! but if I open it - there is only one page! the last added page! all I need - to see all of the added pages.

what am I doing wrong?

thank you very much!