If you're interested in using a commercial product the LEADTOOLS SDK can perform this conversion for you. They have Xamarin libraries available for DocumentConversion.
https://www.leadtools.com/sdk/document/document-converter
The conversion also takes place on the device where the libraries are, so no internet connection is required. The libraries can handle conversion to and from PDF, DOCX, and various other office and SVG formats. Here's a code sample showing how to convert an input DOCX file to an output PDF.
using (DocumentConverter documentConverter = new DocumentConverter())
{
var inFile = Path.Combine(ImagesPath.Path, @"Leadtools.pdf");
var outFile = Path.Combine(ImagesPath.Path, @"output.docx");
var format = DocumentFormat.Docx;
var jobData = DocumentConverterJobs.CreateJobData(inFile, outFile, format);
jobData.JobName = "conversion job";
var job = documentConverter.Jobs.CreateJob(jobData);
documentConverter.Jobs.RunJob(job);
if (job.Status == DocumentConverterJobStatus.Success)
{
Console.WriteLine("Success");
}
else
{
Console.WriteLine("{0} Errors", job.Status);
foreach (var error in job.Errors)
{
Console.WriteLine(" {0} at {1}: {2}", error.Operation, error.InputDocumentPageNumber, error.Error.Message);
}
}
}
You can grab all these in a NuGet package if you prefer.
https://www.nuget.org/packages/Leadtools.Document.Sdk/
Note I'm an employee of the company which makes this product. They also offer free technical support for the product.