Section/category setup input
You need to create several inputs and apply them to your topics category group. 


Description field 
Assets field for PDF's  
Matrix field that allows the user to add multiple FAQ's


In your Services detail page get the category from your category input and output the description: 

{% set topic =  entry.categoryInputHandle.first() %}
{{ topic.descriptionFieldHandle }}


Next in your Resources detail page grab the category and output the PDF and FAQ's. 

{% set topic =  entry.categoryInputHandle.first() %}
&lt;a href="{{ topic.assetFieldHandle[0].url }}&gt;PDF&lt;/a&gt;
{% for faq in topic.faqMatrixFieldHandle %}
    {# output the different fields you setup in the matrix… #}
{% endfor %}