I have an method and it converts pdf text into a list. After the process the memory usage increase too much. For example a 1000 page pdf use 300mb memory and i can't free it. I have readed some LOH articles but have not find a solution.

```
 public List<string> GetTextFromPdf()
    {
        if (_pdfDoc.Pages == null) return null;
        List<string> ocrList = new List<string>();

        foreach (var words in _pdfDoc.Pages.Select(s => s.Value.WordList))
        {
            ocrList.AddRange(words.Select(word => word.Word).Select(input => Regex.Replace(input, @"[\W]", "")));
        }

        GC.Collect();
        return ocrList;
    }

```